3) Infantry armor. It's cheaper than you think. Divisor 2 armor is in three places in AToW: Davion and Lyran Armor Jackets, and Ballistic Plate Vests. All three don't slow you down, and make you much harder to kill.
I think the Marian Infantry Kit does too, and it has like a really good helmet, all for a good price. I want to say in Megamek you can also get that 2 divisor with a marine combat suite.
The other thing I'm not sure has been mentioned is that Infantry is really good for scouting out buildings ahead of your Mechs/Vees to see which buildings have basements or not. I like fighting Small town maps in Megamek with some woods, water, and elevation changes, with random basements. If I know that during the fight one of my big boys may have to smash through a building, I'll try to jet some jump infantry in that direction to check it out first.
Between the spotting for indirect fire, and the scouting of buildings, I feel it is almost irresponsible not to have some infantry in your unit.
It's too bad that Princess seems to have real hate on for infantry, I don't know what in the programming drives it, but it seems that Princess will go out of its way, and ignore beefier targets if an opportunity, to blast infantry in a building appears, even if they are halfway across the map
