If you stick to the SOTE novelization only you could keep to those basic figures or if you also like the comic book adaptation you could pick up even more characters to develop. Here are a few I would like to see, but of course this is simply my opinion...
Spiker
Guri
Leia as Boushh - a better version
Koth Melan
Spero
Benedict Vidkun
Anyway, just some ideas I thought I would throw out.