I think it'll slow combat down just a touch.
Not overly worried about that with 5e Theater of the Mind.
And you're right characters with reaction defenses will be tougher to hit, if they burn through those resources faster. So if you have a party with a lot of wizards with shield and fighters with parry, you may have some workday issues. Or not.
I'm more thinking of defenses like the rogue's Uncanny Dodge, whose only limiting resource is the reaction it spends.
I'm interested to hear how it goes once you've had a chance to try it.
Thaumaturge.
If it happens, I'll be sure to.
Yes, unlimited reactions throws balance out of wack...
There are classes/feats, where players will gain far far too much utility/power. Other classes barely use reactions.
For instance a battlemaster with both polearm mastery feat, and sentinel, along with their riposte will for sure outshine the rest of the party where they feel they are just minor character's to that fighter's party. Not to mention Defensive duelist as well. Shield Mastery Feat...
My PHB is on loan at the moment, so I can't reference particulars outside of basic just now. That said, reactions still have a significant limiting factor; they are
reactions to things that happen and, as such, are inherently circumstantial. Or, at least they should be.
Anyone with the Defensive Duelist feat would basically get their proficiency bonus to AC all the time if there were unlimited Reactions. That seems pretty powerful.
Yes. And coupled with Uncanny Dodge, crazy. But if these generally always applicable reactions are outliers, I might be more comfortable adjusting them on a case by case basis to make them more circumstantial.
Perhaps, just allow an option that will enable sticky characters to become more sticky, rather than letting everyone have unlimited Reactions. Say, add a bullet point to the Sentinel feat that gives an extra reaction per round that can be used for Opportunity Attacks only. Or add something similar to the Fighter class as a fighting style. It could maybe even scale with attacks, so that you have one Reaction/OA for each attack you possess.
Just some ideas.
I wouldn't do that, for balance considerations mentioned already in the thread.
You may consider allowing OA 1/turn, with the clause that as soon as one is performed that burns the reaction for the round. Still you should expect some spikes (thinking about a rogue Sneak Attack for instance).
Alternatively you may try with allowing as many OA per round as the number of attacks available through multiattacks. But that involves a tiny bit more tracking.
I like these options for fighters, specifically. But my problem is the monk. Or more, specifically, my brother's problem (as with every edition) is that the monk has flavorful features, but is built to play like a striker, rather than actually fighting with wisdom (that is, reactively and with the ability to interrupt and deflect opponents' actions).
I think I have a solution for that, though:
Every character gets one reaction, as normal, but can forgo taking any action on their turn to gain one additional reaction per attack they would be entitled to with an attack action. Effectively, they would be entering a readied stance that they could shift into or out of round by round, as desired.
