Can i use gsn for any token in my CEX ( Centralised Exchange )?

Hi! by reading the documentation on opengsn; I was able to understand that to use the gsn, you have to modify the token code. What about tokens that already exist?
I want to use the gsn on my CEX to allow users to pay the gas fee during withdrawals with the token they want withdrawn. (ERC-20, BEP-20 …). How to implement this? since I will not be able to modify the source codes of all the tokens that will be listed on my exchange.
Best Regards

A GSN request goes from a sender (EOA) to a receiver contract.
The sender doesn’t pay for the request (another contract, the paymaster pays), but as a result, the receiver must be aware the request arrived through a meta-transaction. This “awareness” is by making the contract “is BaseRelayRecipient”.
The only way to work with genera-purpose contracts is make the recipient a wallet contract - that is, always go through this wallet and call other contracts (e.g. tokens) through it.
GnosisSafe and Argent are examples of such wallet contracts.
If your users use normal “EOA” addresses, then GSN can’t help them use plain, non-GSN-aware tokens.