I've seen the thread about payout options. A related feature that would be very nice is if credits not yet paid out could be used to purchase things on itch.io. It seems a bit silly having the overhead (both administratively and actual fees) of getting money paid out from itch.io and then more overhead to getting money into itch.io, when this double overhead could be bypassed by letting one feed directly into the other.

I agree. Solutions should be implemented, even though I havent put anything up for sale yet. But - I would've assumed your idea was already how it is. I guess not.