Class != role.
Every soldier has a complete personal row consisting of background perks, faction perks, a proficiency perk and class perks.
Class A multi classed to B is different than B+A.
Single class soldiers are viable.
= endless possibilities.
http://wiki.phoenixpoint.com/Terror_from_the_Void#Classes
E.g. for scouting:
High mobility. -> armor or mutations or augmentations granting speed. Dash (Berserker). Quarterback (Assault). Volunteered. Tunnel Rat. Battle Hardened (PX faction).
Jumping. -> Jet Jump (Rocketeer or Heavy). Jetpack Control (Heavy). Propeller Legs.
Unseen. -> Tunnel Rat + Infiltrator.
Awareness. -> Mind Sense (Priest). Motion Detection Module.
Vehicles.
Spider Drones.
Mind controlled enemies.
…