Yes, I could see a lot of GMs being interested in plug in and go product that fills that niche. Implementing the right feature set is challenging, as existing dedicated virtual tabletops have already shown. But something like a simple Owlbear Rodeo extension that adds basic miniature recognition might be all we need.
Sure! It's smallish, but ttrpg players are accustomed to filling in with their imagination. You might even have a pan feature that would shift the map and show markers to help minis get replaced correctly. This might help with the size problem a bit.