It seems like the Elite and Heavy slots are limited atm, but both factions got their first elite fairly recently.
operatives are another category that could use more, but they have been added to very recently.
Commander seems fine for Republic, but a likely choice for next Separatist.
what do you expect? I have personally been trying to figure out the next heavies for the 2 factions and I expect Separatist to get the Hailfire droid because the size fits perfect with the size of other legion vehicles and its iconic.
What will Republic get? most of their vehicles are too big, and I doubt they will give any spacecraft to avoid stepping on X-wing.