Ability for token-denominated Fee to be paid to Relayer

Hello,

In GSN meta tx, is there a way for the user to specify in their offchain signature a value like:

token_fee_amount

That will skim a small amount of tokens off of their tx and pay them to the msg.sender; the account that is relaying their transaction?

If not then you guys missed a HUGE opportunity and I really really hope that you add this feature in your standards. This would allow relayers to collect fees in terms of tokens and even set minimum fees in order to stay profitable and be totally decentralized.

This way you can ditch centralized paymasters all together !!! Relays would only relay a tx if they are being paid enough # of the ERC20 tokens.

One of the use-cases we see for GSN is “pay-with-tokens”: a way for users to work with tokens, without any ETH.
For that,Paymaster that accepts tokens from the user, convert them into eth (so it can pay the relayer for making the transaction), and letting the user call its target method.

We have a sample TokenPaymaster that attempt to demonstrate how this can be done.