Regarding part 2, if open topped transports were supposed to be used as you claim, they wouldn't allow to shoot ALL weapons from out of them.
But they do, ever since the first game, its as intended mechanic as it can be.
Why? They should be able to shoot out of them - they should be just less effective than when standing on the ground. Sometimes it is better to leave a building and shoot as it has too few windows. Halftracks shouldn't be better shooting platforms than buildings (again the 'feel' of the game is lost).
In coh1 there were kangaroos (also a rather specific idea looking at how many squads you could place there).
I just feel that halftracks' in game utility should be their support of 'ground' troops. The number of abilities and upgrades should boost/help surrounding infantry rather than make them more mobile. They should be the nucleus around which infantry units operate - not a lightning speed turbowagen with ridiculous number of infantry entities crammed inside and still shooting better than when fighting on the ground.