well~ if you just want people to feel better walking along the streets, your idea is a pretty good one~ all i want is just to see people walking on the street.
if you think... people are gonna walk by there anyway, why not make it prettier, i absolutely agree with you! and as you said, "this seems like a semi-easy creative quick-fix to the problem.", it's a really quick-fix!
what if less and less people would be around? i don't take people walking by for granted, and certainly don't expect people coming just to see the window artworks. how many people would come to downtown if it weren't for work/school? and if those things disappeared in the future? forgive me if i'm not so optimistic on this issue. i do hope there are still people walking by 10 years later. and i do hope they are not just window arts but real store/office/apartment. there gotta be a reason for people to come, work, live, entertain, you name it. it won't change over night, but if it starts now~ the future we'd like to see will happen sooner~ ;)