We've created a copy of eosio.token to issue our own in-game token.
Going forward we might want to add our token to the crypto exchanges.
Question: Given that this token was created by our own copy of eosio.token, will Exchanges be able to utilize this token?
As @confused000 suggested you can use your own copy of the contract and you can use the existing copy provided by eos. I have achieved the similar by the existing copy of the contract and it is working fine you can also add or remove the functions as if it is your own copy.
eosio.tokenauction mechanism is available yet so you need to use your own