Depends on your view of things. I can see another level of gameplay that can be considered if one could switch between soldiers.
Example one, say a squad has a mission to destroy a base. If the player gets killed, he goes onto the next player of the hit squad and so on until the mission is finished. Example two, friendly AI can be annoying at times especially when you are trying to set them up in the right position for an ambush or scout a direction. If you could switch between the team units, you have the OPTION of putting the units in the right position quickly (like in Ghost Recon) without them running or moving in the stupidest ways which often gets them killed.