The ERC-6909 token standard is a new token standard that was adopted by Uniswap v4. As specified, the SuperchainERC20 bridge will not work well with ERC-6909 tokens. We do want a world where it is possible to bridge these tokens across the superchain natively.

Perhaps an easy solution is to rename the SuperchainERC20Bridge to the SuperchainTokenBridge and then add the following functions:

function sendERC6909(address _tokenAddress, address _to, uint256 _id uint256 _amount, uint256 _chainId) external;
function relayERC6909(address _tokenAddress, address _from, address _to, uint256 id, uint256 _amount) external;

This is not a blocker for going to production but could be a pretty straight forward addition to the contract during a future upgrade.

Renaming the contract to be a more generic token bridge would also make it possible to support ERC721 tokens or really any token standard without needing to introduce new predeploys.