I don’t see the point of this. Original never had it and vehicles are godly for their cost. It’s NEVER a consideration “soldiers or vehicle” it’s always “bring a vehicle on nearly every aircraft with a weak squad, match the teams with the vehicle, and bring multiple aircraft if the mission calls for it”. Considering how easy it is to field multiple aircraft, I’d say work on fixing that portion of the game before once again making things even more mindless.
If you want just soldiers in a mission, bring two aircraft or swap out the vehicle. What’s difficult about that? Why must the game facilitate you never having to return to base?