A button to completely freeze the game, I do not mean the pause button, I mean actually that there should be a button to stop to everything happening in the game in order to consider a next move.
Endless mode in PvZ was always so frustrating because so much would happen at once and once one single lane got breached, I could never repair it in time and that would put an end to my runs. This, similarly, would benefit from a feature that just lets you freeze everything in case something goes terribly awry.
With that said, it does not need to be built directly into the gameplay, it could be an item that you can purchase, I would definitely buy it.