UC / Bren Carrier:
Easy fix that would make the UC more useful in early game strats (low tech strats):
1) replace IS starting unit with an engineer squad, adjust manpower accordingly
2) make healing available without tech
15 fuel and munitions upgrade is only too expensive because brits have to tech up early for healing, repair and mine sweeper(situational).
All the other factions can repair and clear mines from their starting unit, brits need tech for this as well. I guess they are tough like that, mine sweeper? Nah brits don't need that 
Making the Med kits available without tech isn't really balanced if you think about the timing of healing of other factions as they all have the same timing it takes you to tech up as Brits (30 fuel isn't much at all and 15 Fuel for a UC only delays it by maybe half a minute) compared to 60 Muni for Ostheer, Ambu for USF, Etc. Likewise the Brits can get out a Sapper just as fast with that teching as well. If you "rush" a Sapper out there maybe be just 1 or 2 mines out at that point if your opponent is mining early.
Personally I'd rather see squads being able to fire out of the UC (it's less of an issue now that they have toned down the Tommy's cover bonus and damage). Its another way to give it utility. Other than that I think they just need to increase the flare throw range for base howies and maybe give their aoe a slight buff (or reduce scatter a bit). I find the Brits lack of non-Mortar Pit indirect fire a lot more of an issue than light vehicle play now that AEC was buffed.