How many packets per second will a pi route?
From professional experience, I can tell you that the average routing hardware (typical OpenWrt routers) will not be sufficient to actually handle the load from only a few dozen users sharing a simple DSL connection.
I've resorted to mikrotik hardware for that reason. You might want to have a look at their stuff, just a suggestion.
Edit: also, maybe if you just setup the pi as a RADIUS server, you could enable bitcoin payments for practically all the generic hotspot solutions on the market.
Not sure what the limit is right now. Will be testing with maybe 5-10 users shortly but .... if it's that busy then I would state that is a sign of success and therefore we can dedicate more time into making a more efficient hotspot.
Guys, if you think that he's doing it wrong, then do it yourself. Otherwise leave him be to make his own discoveries.
I'm not saying he does it wrong. Just giving advice from a few years' practical experience with hotspot solutions in hotel environments.
The longer I think about it, I'd absolutely suggest a bitcoin RADIUS server. That would scale very well with OpenWrt access points and whatever DSL router you might wana use. Could probably become a top-seller when it's combined with a small display, thermal printer and a few buttons to produce hotspot tickets as well.
Edited because I f***ed up the quotes.