I will likely go back and forth on whether the S1RII appeals to me but I recently was reminded not to lust after gear. I've got an S1 and S1H currently and I bought an S5 and eventually an S5II hoping to replace these, sensing size and weight were the only real drawbacks of the S1 bodies. I sold both the S5 and S5II almost immediately, for usability reasons (worse viewfinder and screen) and because of the picture being over-sharp on the S5II.
I had somehow convinced myself that a newer camera would spark my creativity, as I am currently in a creative rut. This was misguided.
The S1 and S1H are still excellent cameras and they produce an image that feels special to me still. They also feel somewhat indestructible compared to the S5 style bodies. I used them primarily to film a major documentary, along with a GH5 and a slew of other cameras over the years including Canon C300 marks I & II, 6D & 5DIII.
In color correction, I learned how little the camera matters compared to what you capture, outside of the quality of life improvements and build quality (the C300II actually broke from use at the hot shoe mount). Even some quality of life improvements should be met with apprehension. IBIS has ruined some of my shots with weird motion artifacts - the days of a loupe and hand grip on my 6D netted some pretty stunning motion.
Among all the cameras I've shot with, I found the most usable camera overall was the GH5 - and if I was to embark on a similar documentary project today and had budget for a new camera, I'd probably lean towards a GH7 for its versatility and portability. I think the GH7 actually represents the most unique value proposition in Lumix's line - for run and gun documentary, with 32bit audio and a 12-60 or 12-100 lens, I don't think it can be beat. Of course, I don't want to go through the process of re-acquiring all the MFT glass and adapters I've now sold.
For me, the S1RII's reduced size and weight, improved high ISO performance, 32bit audio would be significant quality of life upgrades - but the trade-offs of higher heat sensitivity, lower battery, and a huge hole in my wallet would not be worthwhile. I mean, I'll want one, as is the case with every new camera I see, but will it actually improve my work? Not at all.