If your squad has AP or AT mines in their inventory, you would be able to look at a spot and give the order to drop that type of mine there. This solves the issue of having to switch through each character in the squad to place their mine.
In addition, have 2 additional options regarding TNT (as all campaigns will be getting it in upcoming update). One button that tells a member of the squad to place TNT in that location, and the other that will order all squad members with TNT placed to trigger it simultaneously.
At least on console there seems to be a pretty good uptick in how many mines are being used. This would help speed up placement significantly.