Giving Patrons the option to “charge up” so to speak to avoid processing fees while gracefully falling back on the current approach might be nice. Making it mandatory however would alienate some people (and we just had that in December ;)), we don’t want that. The fall back IMHO is crucial here, to avoid the need to constantly having to top up.
What I don’t like at all to be honest is creating some kind of parallel economy with some custom Patreon currency (be it crypto backed or something like Nintendo Points back in the day). That becomes intransparent too quickly, regardless of how easily it can be mapped to something like the $ (or € for that matter ;)) and also creates a whole rat’s tail of further issues that IMHO shouldn’t be something that Patreon, our Patrons or we should have to concentrate on handling. It’s bad enough as is for people who don’t happen to live in the US like me who constantly have to have an eye on the current exchange rates. (BTW, would be great if you thought about offering the Euro, but I know that’s taking this off topic)
Having some kind of wallet charged up with funds is basically how Liberapay works, and they circumvent the fee madness nicely that way. What they don’t do is having a fallback solution in place to fetch funds for pledges from some other means of payments if they aren’t sufficient for the current payment cycle, but it does create the situation outlined above where patrons don’t remember or care to top up and there goes your monthly income.
If Patreon were to implement this, it should work pretty much identical to how our creator funds work today. In a nutshell: Enough funds? Use wallet. Not enough funds? Take difference from primary payment method.
And what worries me is the psychological component mentioned by @trevor.mahlmann - I’ve also made the experience that “one time donations” create a whole different kind of attachment to the cause that’s being supported than having a renewing monthly support, making retention way more difficult. The approach to do something like a “be charged annually” as mentioned by @colortheory might combat that though.