Hopefully this idea can be relayed to the Devs, @Fox told me to post it here.
In a new game mode of PVP (Raid format?), we select 5 of our monsters in a squad, and the game will randomly pick which 3 of them will start the battle.
On each monster's second turn, you can choose to 'tag out' and select which of the 'reserve' monsters will 'tag in' in its place.
This also happens when one of your monsters dies... you choose which of your back up monsters comes in next.
A cool fact about this game mode is that you may not have your denier(s) in the starting line up to begin with, so the notion of fastest denier wins the game is lessened drastically.
Worth an experiment at least? If not, what's the problem?