I read carefully this very long thread

I feel you need to consider the aim of the game is to port dnd to a video game format while making it accessible and flow well.

Solasta system with reaction is faithful to the rules but not accessible and poor in terms of flow (let's face it sometime I would even rather avoid an encounter becaus EOF the clunkiness). Also consider if MP would be twice as many pop up (prepare to refuse caster to your party).

Because DM are the reason why reactions work in dnd, the only practical solution imo are presetted readied action. I posted overwatch as a well known tactical RPG example but then it would always be an imperfect solution (e.g. shot the first enemy in my line of sight vs. shot that goblin with low hp if it enters my line of sight and ignore the others)

Considering Larian they would (and should) favour accessible contents to 100% implementation.