imo commander alrdy has enough, bia, repair, camo, 6e sense, view range, sometimes the radio skill with view range, and mentor (10% more crew skill) and the skill it can replace other crew are also not bad, radio man and loader are the ones getting shafted
ps: and stuff like dead eye and designated target are kinda useless due to it beiing perks, i train that as 4e, then u never reach it, making it useless