Rental equipment tends to get abused, so I'm thinking that the consumer circulators will have pretty short lifespans. The library should probably budget for replacing the things every few months.
The alternative of lending professional circulators probably isn't too appealing, since they tend to be so much bigger and heavier. And they're equally vulnerable to death by drowning.
I think it's a great idea, at least as an experiment. I would have loved this. I made my first forays into s.v. with borrowed equipment, but was lucky enough to know people who owned the stuff.