Too many pop-ups slows down combat. I think WolfheartFPS had a good idea regarding this in that chosen enemy to react to would be better and not slow things down too much.
I am not convinced that's necessarily true. With multiple characters having to set up multiple reactions for specific characters it might get very tedious, or not that much different then it is now - meaning not getting bothered with it.
A preset system doesn't mean that every combat you have to set new parameters for every character. Most presets would not change from encounter to encounter.
I set AOO preset for Gale to Off because I don’t want him wasting his reaction on it. He sucks at melee anyway. So AOO preset remains off for every encounter until maybe one occurs that I change my mind. Instead, I set Shield spell to On with a preset to only trigger if an enemy hits Gale. All Enemies. So, whether Magic Missile or any enemy shooting Gale or hitting with melee, he will cast Shield and ONLY if by casting it he will cause them to miss (so they hit by 5 or less). You took maybe 10 seconds to set your presets for Gale and don't change them from battle to battle because you really have no reason to.
I set Lae'zel's AOO to All Enemies and leave it as All Enemies for most encounters because she has no other reactions. Therefore, she will AOO on the first enemy who might trigger AOO in every encounter unless I am fighting against someone important - like let's say Ragzlin. In an encounter against him where I want to make sure he in particular doesn't get too close to Gale, maybe I switch it to AOO for specific targets like Ragzlin and maybe a few other heavy hitters. And that’s still a maybe that I'd switch it.
And let me point out that AOO would default to All Enemies in the beginning, so I might not ever mess with Lae'zel's reactions. We're talking very minimal player management here and pretty much the same results as constant prompt system where 9 out of 10 times you'd AOO anyway on the first enemy to trigger it because few actually trigger it in a single round anyway.
Shadowheart would be exactly the same as Lae'zel because she only has AOO as a reaction.
Wyll is the same as well. No other reaction but AOO.
Astarion is the same. Nothing but AOO.
The entire EA, up to level 4, you might change your presets a few times maybe, if at all because most battles you would not have a reason to. No pop-ups or prompts needed because you don't need them. You'd say yes every time anyway.
Now, at level 5, that's when you might get a few reactions that would be tricky, like Counterspell and Uncanny Dodge, and presets for these select few might take a bit more time to set ahead of time or might require a bit more tweaking during combat. However, we’re still not talking about gobs of time to manage them. A minute maybe on Counterspell if you can't decide which spells you do and do not want to be bothered with reacting against. "Should I counter Darkness? Should I not?"
And as stated numerous times, Uncanny Dodge could take no time at all to set a standard preset that handles your reaction. You may or may not turn off AOO at this point and set Uncanny Dodge to only trigger if damage done to you is above a value that you set. BOOM. Done. 10 seconds maybe?
My point is that we're not talking "multiple characters having to set up multiple reactions for specific characters" unless YOU actually want to use that Selected Targets preset for some reason. Not every encounter would require such reaction finesse.
Prof. Dr. Dr. Mad S. Tist 
