Currently the reaction system is clunky with only attack of opportunities availables.
Dnd 5e had the concept of ready-ing an action to be able to use it as a reaction during the enemy turn.
You would tell your DM if X happens do this action at the cost of using your (bonus) action for the current turn.
It is hard to implement in a video game but one concept pretty much any tactical RPG has is for ranged dmg dealers (e.g. archer, wizard) an overwatch system (e.g. xcom)
Essentially you would position your archer / wizard use as an action "ready an action: shot an arrow or use that cantrip" and then the first enemy entering the line of sight of your character will trigger the attack as a reaction.
Simple & proven this classic tactical RPG staple (and dnd 5e compliant) will add dept to encounters (if half of the goblin camp enters in overwatch you would think twice before charging head on!) And it is bringing us middle of somewhere for a more diverse reaction system.
(Still would love more option beside overwatch: to ready an action for feathered fall and automatically trigger it if one of my companion get pushed)
