There some technical works to discuss before adding coins to exchange and also need to make sure wallet is free of bugs. i think there will be a coin listing charge too for there effect, and exchanges like nove need community vote and rating system to add coin for there exchange
What type of tech work? I think they simply can use an existing wallet system for any new coins just like how you can add any new token to MyEtherWallet. I guess underlying software of Wallets are all the same because they're all working with the same Blockchain.