That was my question a few days ago. Then I clicked on the "plus" sign after pruchasing a BN. I like the method now that I know it as said above it keeps the command link.
Also when our purchasing individual vehicles or special units make sure the unit you then attached to (ie: BN,Co, or Plt commander) is highlighted. Important for C&C
It's a backwards way of purchasing but I see why it's that way and it works perfectly.
So much fun..you have a few minus points and need to cut someone...but from where:)
Every point matters so some units will have less experience etc and even swap a HT out for a jeep or even a cheap truck.
It's my favorite part of the game.
I just wish it was connected to a campaign.