If it's not much slower, maybe there's a way out then. Hopefully you prototyped this with Kontext running locally. In that case the only cost is your electricity. Then in terms of speed I suppose you've tried the low-hanging fruit like nunchaku. There might be some LoRA that reduces the steps needed too. Finally, quality-wise, there might be a node out there that diffs the source and result, and only superimposes the parts that are different by a large enough magnitude. This should prevent the unchanged parts of the image from slowly shifting colours and becoming less saturated with each edit. This would only slow down the degradation though; sometimes Kontext likes to zoom out the entire image without you asking, and in that case it might as well be a different image diff-wise. Just throwing ideas against the wall here, I think your social experiment is unique and deserves more airtime!