I was doing some research on implementing automated cowswap orders (they have an SDK) and I realize that we can do something pretty cool:

1. Only support settlements using UUSD.
2. Allow the user to configure what asset they want to be paid in, it should be saved in localStorage.
3. The cowswap quote can appear in place of the reward amount. For example, by default, loading the app for 100 UUSD permit would show that. But if the user configured to get paid in USDT, then it might come out to something like 99.5 USDT. The app will simply display 99.5 USDT instead if their settings are set as such.
4. The claim permit button would actually 1. invalidate their permit (if the wallet can afford the pay out) 2. initiate a cowswap order with the beneficiary address set to the permit beneficiary

Then now we can enforce people using UUSD in the backend but user facing they can receive rewards in any asset they want!

I think this provides best of all worlds for users. For partners, we could charge a premium for them to use other tokens natively in the background etc.