I agree with letting the enemy's do their turns at the same time, and i think the suggested way sounds great, tho 1 small change, let us choose it per combat encounter while we are fighting? Some battles i really want to see all the movements, and some battles i just need the enemy to get on with it so i can kill it when it's my turn.
Yes, the concept is good, as long as we don't actually care to follow what enemies are doing.
A tricky bit might be that action sequence is impactful - if someone casts a debuff, or buff knocks your out etc. it changes chances to hit of following characters etc.
