I ordered my AIs to crew the tank with only my friend inside. So we had a tank with human commander and 4 AIs from the different squad.
In short: it’s complitelly useless option.
The tank was as operable as with one crewmember. My friend had to switch seats to operate the vehicle.
Either remove this option or allow to use this AI as a “normal” tank crew.
You may argue that they are all infantryman, not tankers, but somehow they work fine when I’m the commander.
The other option would be to introduce special infantry squads that are focused around tanks and their soldiers are able to operate those vehicles. Not as effective as tankers but still. Although I have no idea how realistic is that.