I.E "flip side with opponent"
=> use your bonus action to move behind your opponenent.
=> Dexterity check VS ennemy AC
=> Success : beautifull and immersive combat animation that leads you behind the opponent (increase the TB system that is actually so static)
=> Fail : Disavantage to your next action.
THIS is tactical options, this is a "custom" D&D (and FR) mechanic that suit a video game and it didn't break any D&D mechanics.
I like this suggestion. Even better use Acrobatics check, which is useless skill now. Also using Athletic checks on climbing to get some kind of high ground advantage (for example in form of ignoring half-covers). There is lots of creative ways how implement advanced stuff while not break the whole DnD mechanic.