I agree completely, and not just bags but every kind of gear - cameras, lenses, tripods, all of it. There must be lots of people who have big collections of these things so why not share them around. They'd get used and beautiful pictures might be made.
I have a ton of lenses and film cameras, bought for their loveliness and for a desire to try them out. I've sold some of them but for the majority I just can't let go of them, psychologically or materially.
I lend my gear out to people I like and trust and have never had problems. If you set up a formal library you could charge membership deposits or bonds to cover damage, or maybe call for character references from magistrates or something (references from their mothers don't count).
I think though that such a library, based on goodwill, might best be restricted to amateur users or otherwise it turns into a hire shop. Let's set up these libraries in every town where there's more than two RFF members!