CineAlta

It is fighting physics.  There are manufacturing limitations when grinding and polishing glass as well as manufacturing limitations as to how perfectly you can align and space each of the elements correctly.  Optical designers only have a limited range of glass types to use.  Eventually tolerances, manufacturing limitations and material availability/costs mean it's a technical and/or economic impossibility to match the performance you get from a simple longer/slower lens on a bigger sensor.  If sensor size didn't make a difference to the image we wouldn't see Arri, Sony, and RED all moving to FF / VV and bigger as their flagship camera systems.  

The weight translates into the way motion is rendered in Dunkirk. The physical effort of the camera operators when handling the cameras and mechanical requirements put on the rigging of such cameras has more of an aesthetic impact than the format size, lenses and film stock combined. Dunkirk and The Hateful Eight both felt significantly lower resolution than contemporary movies shot on Red and Alexa but had a physical movement quality that made them feel like real movies rather than a string of 0's and 1's. Film schools should be teaching people information like this

The weight translates into the way motion is rendered in Dunkirk. The physical effort of the camera operators when handling the cameras and mechanical requirements put on the rigging of such cameras has more of an aesthetic impact than the format size, lenses and film stock combined. Dunkirk and The Hateful Eight both felt significantly lower resolution than contemporary movies shot on Red and Alexa but had a physical movement quality that made them feel like real movies rather than a string of 0's and 1's. Film schools should be teaching people information like this

Sony NEX5N or NEX5R or NEX5T all make very nice pictures and are priced at around 150eur for a body. Screen flips and can accept a loupe too. Tech heads will moan about the avchd codec but it's the same codec they gave c100 and fs100 users for in body recording. Add a focal reducer adaptor and he will have an extra stop of light and will gain full frame field of view from your lenses meaning a basic 35mm/2.8 russian lens will become a 25mm/2 lens.   
Focal reducer: https://www.ebay.es/itm/Focal-Reducer-Speed-Booster-Canon-EOS-mount-Lens-to-Sony-E-Adapter-NEX-7-5-A6500/351338788897?hash=item51cd6c7821:g:SFoAAOSwBahU~~~G     That's quite a bit under budget and will allow a nice variable nd, some spare ex-pro batteries and will work with even the cheapest sd cards.
edit~~ Additionally all of the above cameras shoot up to 50p in full hd. Slow mo is a nice addition

Sony NEX5N or NEX5R or NEX5T all make very nice pictures and are priced at around 150eur for a body. Screen flips and can accept a loupe too. Tech heads will moan about the avchd codec but it's the same codec they gave c100 and fs100 users for in body recording. Add a focal reducer adaptor and he will have an extra stop of light and will gain full frame field of view from your lenses meaning a basic 35mm/2.8 russian lens will become a 25mm/2 lens.   
Focal reducer: https://www.ebay.es/itm/Focal-Reducer-Speed-Booster-Canon-EOS-mount-Lens-to-Sony-E-Adapter-NEX-7-5-A6500/351338788897?hash=item51cd6c7821:g:SFoAAOSwBahU~~~G     That's quite a bit under budget and will allow a nice variable nd, some spare ex-pro batteries and will work with even the cheapest sd cards.
edit~~ Additionally all of the above cameras shoot up to 50p in full hd. Slow mo is a nice addition

Second hand Sony A5100

Unless you're renting an entire set there's not much point.  Low end modern zeiss glass isn't very exciting (even the cinema variety).  Until you go to Ultra Primes or Master primes they're all pretty dull and lifeless.  
Rent a 28mm Otus instead.  Now that's a cool lens on both aps-c and full frame!

Unless you're renting an entire set there's not much point.  Low end modern zeiss glass isn't very exciting (even the cinema variety).  Until you go to Ultra Primes or Master primes they're all pretty dull and lifeless.  
Rent a 28mm Otus instead.  Now that's a cool lens on both aps-c and full frame!

Cinema lenses aren't much different to stills lenses in terms of image quality until you go vintage primes like k35's, old superspeeds and lomo zeiss copies or go for the top end like cooke S4, Zeiss Master Primes or Leica C-Summilux . 
OTUS lenses are available in nikon mount and at £3000 to buy, it is well worth renting for a few days to get a taste of the sharpest most refined 28mm f/1.4 ever.  It's a manual focus lens too, so focusing is really nice for video.  Most try before you buy style camera rental companies will have otus lenses in stock and it will probably be similar rental price to a zeiss compact prime.  
I suggest spending your money renting an OTUS because it will genuinely be an interesting lens to use for someone experimenting.  Just be warned you may end up buying one after using it for a few days. Insane lens. 

Unless you're renting an entire set there's not much point.  Low end modern zeiss glass isn't very exciting (even the cinema variety).  Until you go to Ultra Primes or Master primes they're all pretty dull and lifeless.  
Rent a 28mm Otus instead.  Now that's a cool lens on both aps-c and full frame!

It may be worth going to the AbleCine website and going through their blog entries. If I recall they used to have a number of very nice F3 S-Log luts available as well as some good information relating to processing the original S-Log curve. S-Gamut was only when the F65 was released to coincide with S-Log2.
There are lots of S-Log2 luts around which will only need very fine adjustment if used on F3 footage. Throw some onto the footage and have a play. I expect they'll get you close.  

A pair of good quality 1x1 led panels from Aputure with 95+CRI to bring the inside lighting up by a few stops.  Fire one up at the ceiling and use the other to simulate the feeling that there's light coming from a window out of shot.  With $900 invested in a pair of LS-1 panels you'll be laughing.  

The video assist won't accept 4;4;4.  It will probably give you a green tinted image if you send 4;4;4.    for use with the video assist, set the f3's sdi out S-Log 4;2;2  Use SDI output A, not the 'Video Out' bnc connector.  If you're set to 24p you should be sending 24p out of the sdi.  the BM video assists seem to sometimes detect the wrong frame rate - on the A7 series they see a 25, 24 and 30p signal as 59.98, but when imported into the timeline you'll see the correct framerate.  
It's worth setting the camera to Cine EI mode since it locks you at 800iso and you get the most from the sensor.  correctly exposed you can pull or push the 4;2;2 footage a lot before it breaks up.  Amazing camera.  ps.  watch out for the 'shutter on/off' switch down near the bottom left in front of the flip out screen.  Set to 'off' gives you 360degree and changing shutter angle won't change anything.  catches you out sometimes.
 

The video assist won't accept 4;4;4.  It will probably give you a green tinted image if you send 4;4;4.    for use with the video assist, set the f3's sdi out S-Log 4;2;2  Use SDI output A, not the 'Video Out' bnc connector.  If you're set to 24p you should be sending 24p out of the sdi.  the BM video assists seem to sometimes detect the wrong frame rate - on the A7 series they see a 25, 24 and 30p signal as 59.98, but when imported into the timeline you'll see the correct framerate.  
It's worth setting the camera to Cine EI mode since it locks you at 800iso and you get the most from the sensor.  correctly exposed you can pull or push the 4;2;2 footage a lot before it breaks up.  Amazing camera.  ps.  watch out for the 'shutter on/off' switch down near the bottom left in front of the flip out screen.  Set to 'off' gives you 360degree and changing shutter angle won't change anything.  catches you out sometimes.
 

The video assist won't accept 4;4;4.  It will probably give you a green tinted image if you send 4;4;4.    for use with the video assist, set the f3's sdi out S-Log 4;2;2  Use SDI output A, not the 'Video Out' bnc connector.  If you're set to 24p you should be sending 24p out of the sdi.  the BM video assists seem to sometimes detect the wrong frame rate - on the A7 series they see a 25, 24 and 30p signal as 59.98, but when imported into the timeline you'll see the correct framerate.  
It's worth setting the camera to Cine EI mode since it locks you at 800iso and you get the most from the sensor.  correctly exposed you can pull or push the 4;2;2 footage a lot before it breaks up.  Amazing camera.  ps.  watch out for the 'shutter on/off' switch down near the bottom left in front of the flip out screen.  Set to 'off' gives you 360degree and changing shutter angle won't change anything.  catches you out sometimes.
 

I think you're vastly over thinking things.  the 10bit 4:2:2 into a 300eur video assist is more than adequate and will write to cheap SD cards.  By the time you upgrade to another camera and need the convergent 7q will no longer be future proof and the devaluation will have set in.  

If you correctly expose while using the PMW-F3 in Cine EI mode (native 800iso out of the 3G SDI into a 4:4:4 recorder) with good lenses it will be the closest thing to an Alexa for under 1500Eur.  To use Cine-EI mode you just operate the camera as if it was a 35mm film camera loaded with 800iso film stock.  You expose for your skintones and let the s-log roll off the highlights.  Very filmic rolloff indeed.  The 4:4:4 files will allow you to push or pull by as much as 2 stops.  F3 footage shot in cine-ei 800iso in 10bit 4:4:4 and pushed to 3200 iso with a +2stop boost in post will look better than A7Sii 4k footage shot at 3200iso via 8bit 4:2:2 external recording. 
Also the sensor readout is very good meaning your motion has less of the skew you'll be used to seeing from most 4k sensors.  Good motion response and 4:4:4 at 1080p is better than 4K with skew to your motion.  You can shoot with very flat 4:4:4 s-log profile into an external recorder while recording a nice lutted 35mbs internal file to the sxs card.  The internal recording is very very good and holds up to quite a bit of pulling around in post.