As a viewer, I should be able to select which pokemon I want to battle with after accepting.

[scasplte2]

When there is a pending duel that has been accepted, the kennyBot should whisper the challengers asking which pokemon to use. Once both respond, or a timeout has elapsed, the battle will resolve.

While TMI has the capability to whisper users directly, Twitch has recently begun to require bots to be validated in order to whisper folks as discussed here
https://discuss.dev.twitch.tv/t/unable-to-have-my-bot-send-whispers/21120

Reqs for validation and the rate limits are given here
https://dev.twitch.tv/docs/irc/guide/#known-and-verified-bots

Doesn't seem infeasible once we have something that is more robust and hosted I think.