I mean, it really depends on the trainer and the pokemon.

It will be harder, sure. But in the end it will be a very effective tool I think. I know for a fact Lisette and her pokemon are going to develop specific styles of orders to give to her pokemon. Why? Because in a realistic non-game scenario if you shout something simple like 'Hit 'em with a quick attack' then the opponent can respond a lot easier with something like 'Use harden' or 'Dodge using your own quick attack'

If instead you use a certain word/phrase like "Shock 'em - " followed by snapping your fingers it would tell the pokemon to do a certain move a certain way that the opponent wouldn't likely be able to entirely figure out.

It takes some practice of course, but in a more realistic battle scenario its only natural I think, to develop strategies like this. Other Audio cues and such aside from simply shouting an attack.

Buuut maybe that's just me. In another pokemon RP I had a Ralts teleport themselves and a Kakuna onto the back of a Conkeldurr, using the simple command that basically read "Remember what we did back at the last place? Do it again!" It was quite effective, since the Conkeldurr wasn't expecting it and allowed the Kakuna to get a number of repeated poison stings on him, resulting in him getting poisoned and basically me winning that decidedly lopsided match~