[@Whimsley] I don't think a pokemon should be stuck in the battle the instant they're sent out, but I also don't think the identity of the other pokemon should be revealed. Similarly to what [@PlatinumSkink] said, I think it makes the most sense for the victor to be able to switch out their pokemon, but they don't get to know what pokemon the other person is sending in -- same goes for the loser, they won't know what pokemon the winner is sending in.

Perhaps there could be an overall limit as to the number of times your pokemon can be switched out? Maybe for shorter battles, you can only switch out once. Longer battles, you can switch out a few times... I feel like there's some sort of mathematical ratio we could find there, haha.