in the original SP1, you onl had 24 core units, and 48 total, so fighting with the HQ was normal.
As you have 200 odds core units with 500 max now, and losing the HQ is end-of-campaign, now the unrealistic SP1 tactic of using your field HQ as a line fighting init is pointless IMHO.
If you change away from an HQ element, you lose the "almost" FOO character of that unit. An HQ is in between a normal formation HQ and an FOO for arty spotting.
My HQs always stay in a commanding position at the rear these days, never get into combat (set range to 1
. I do not bother buying them vehicles either. if they need to motor to the rear of a rout to rally folks, I use one of the nearby support arty transports.
Upgrading to a vehicle can be bad - especially if the enemy use air against you and pick you off.
My core FOO though (I usually only have the one, dismounted not vehicle) - I usually motor into combat to pick off some crews etc when safe to do so, in the early battles as the first 5 kills are the ones that bring most immediate increases in combat effectiveness. Other than that, I protect them utterly once experienced as they bring fire in so much quicker, that losing one is a real pain.
Cheers
Andy