There are 20 amino acids... all made in our gut.. I fail to see the argument.

Are you aware of the fact that ALL amino acids are exactly the same in all plants and animals?
The 20 amino acids never change. Alanine is always Alanine, regardless of where you get it, belive me, so any composition could be made easier from plant sources.. If you are not one of the very few with sever chronic gut disease, your guts will do the rest.

And the ones lacking will be produced due to the chemical equilibrium they are bound to...

Again 99% vegans are enough, the few incapable of adapting will have meat, classed as a medicine :) that works?