Aside from all the "payment processor nonsense", I think having an on-site wallet (similar to steam wallet) would be a huge quality of life addition for the itch users, especially ones that earn money from sales on itch, which they can then directly use to buy other things on itch, without first having to wait for a payout and getting the payment processors involved at all (and dodging some fees along the way too). It's an absolute win-win.