Related to Issue #1, it might be possible that the best move a cancer could make would be to reverse a mutation, in reality meaning that a small subclone that didn't get mutation X becomes dominant. This would be necessary if we ever wanted to look for a cycle, where a cancer gets trapped oscillating between two mutually exclusive mutations due to two different treatment modes.
Could also have this from the treatment perspective, could conceive of a mutation which is beneficial undertreatment but a burden in a permissive environment. This is observed in antimicrobial resistance.
Related to Issue #1, it might be possible that the best move a cancer could make would be to reverse a mutation, in reality meaning that a small subclone that didn't get mutation X becomes dominant. This would be necessary if we ever wanted to look for a cycle, where a cancer gets trapped oscillating between two mutually exclusive mutations due to two different treatment modes.