That sounds like a sensible fallback. Keeping the RAW/RAWC master at full-res 60p is the important part, since it preserves the option for proper desktop export later. The proxy can be more pragmatic, especially if the Qualcomm encoder is going to be device/driver dependent.
The HDR30 idea is very interesting, probably more useful than forcing a fragile 4K60 HEVC path on phones that don’t really support it. Alternating exposure RAW frames could give a genuinely different look from the normal phone HDR pipeline, especially if you keep the merge natural and avoid the over-processed local tone mapping look. Would be great to see a test with motion in the frame, to judge ghosting and highlight handling.
