>>38005205ATB in Pokemon is questionable especially given the competitive aspect
Battles potentially being decided by whether you can perform menu selections fast enough sounds like a bad time
I could maybe see a system where you can queue up attacks in advance so they can use them as soon as their action bar or whatever fills up, perhaps with a Stadium style of selecting moves where its mapped to the d pad.
But the other big problem is how Speed would factor into it, Speed is already a dominant stat as-is, allowing fast Pokemon to attack more often would make them even more powerful, especially if you went with the naive method of having a Pokemon that's twice as fast being able to act twice as often.