The limited edition art is really just tracking receipts - you can do that over email if you want and it really doesn't have to be public. Non digital art does fine with private receipt tracking. You can also have a dedicated database that charges art owners a maintenance fee, and tracks who the current owner of each art piece. Basically free tier AWS.
For 2) forever art already existed without any ledger. People store copies of pictures they like because they feel like it. Not being on a ledger doesn't mean Nyan cat will disappear. The ledger might attempt to guarantee that unpopular works stay available, but I don't think you can guarantee that any particular ledger will continue to be active "forever".
They could do a hard fork that prunes out the unpopular art to save on space, and migrate everyone to that one, leaving the old one unhosted. Long term, you're not going to force people to keep spending resources to maintain stuff that nobody cares about