They get mutagen at lv1 pls a rank of sneak attack. The mutagen gives you a +2ac natural armor bonus and a plus 4 physical ability bump at the cost of a -2 to wis int or cha of your choice. So a lot of bang for your buck of a 1 lv dip.
Homeworld 2 is an amazing game and if you haven't played it yet and like RTS games it's worth giving it a go as it has held up surprisingly well given how old it is.