I've seen in some of the videos that the BA had some sort of energy weapon, in the latest one at least. It was when someone jumped up, then shot and killed someone below them, it looked like a gauss rifle effect, except MUCH less destructive, I'm sure. I also saw in the other video, an earlier one, that they had some sort of ballistic-like weaponry.
If you look at the media gallery, one of the advent calenders had the "BA Paradise" picture. It was taken in some sort of bunker, and had weapons lined up against the wall, in racks. I think that shot was somewhere in the range of Calender 80-95. Or something.
I can't view pictures for some reason on this computer, I guess the school computers blocked it...somehow I can still log in and whatever. Maybe IE is just acting up. If it works, I will try to find it, and link you to it.
Doesn't that depend on the size of the mortar? Since this is a game based on fiction, I see no problem with mortars doing damage to mechs. I'm neutral to the idea myself. Mortars might be neat, but I'm not sure they would add a whole lot to the game.
Battle armor lobbing mortars reminds me of the Heavy armor in Tribes.
I'm neutral to it as well, but I think you would have to sub something on the battle armor to acquire the mortar, that's just my opinion.
EDIT!:Found that link, here it is:
http://www.mechlivinglegends.net/cpg/displayimage.php?album=35&pos=87