How does that make a difference? As I understood it, every individual would still have to do a regular on-chain transaction, it's only if you later realize you actually wanted to donate more than you did that this could be useful because then you avoid the full transaction fee. Or if you let it run over years without settling and do a yearly donation, though I'm not clear on the implications there.

Or, if the on-chain parties are just Wikipedia and a few big payment service providers to avoid that everyone has to do the setup individually, you've basically reinvented paypal credits or, less evil-ly, liberapay.