Phoenix Soldiers "multiclass"

Yesterday I was looking the Mailbag #1 (Thanks Julian for the time dedicated!)

In 8:40 the explain the class “restrictions” but he said Phoenix Soldiers can have two classes.
My question is “Those classes can come for the other factions”? Can we have a Phoenix Soldier Assault/Infiltrator or Heavy/Berserk?
Thanks in advance!

if you have the tech and the training facility for that class I wouldn’t see why not.