When forking a chain and serving it, ideally it would possible to configure an overridden Common such that the chain ID is different.

This is useful because a same chain ID will confuse legacy wallets like Metamask, where they will insist that a chain returning chain ID X be added as an alternative RPC to an entry already using that chain ID, rather than allowing you to add a new chain with the same ID but different RPC.

This is a problem because interacting with the fork will change the nonce and force the user to have to clear the activity of an address when going back to interact with the "real" chain that was previously forked.