Then what was the point of even splitting it up in classes? Isn't that a pseudo-example of classes not mattering.
Global Agenda offered each of its class choices a weapon variant and abilities all their own making them all unique.
They made it so only a Medic could heal so it was its own class. Only an Assauly could beef up enough to tank. Only Robotics could build turrets and shields and robots. Etc.
With just an Omniframe and no classes but instead Technology Trees following the Holy Trinity (Tank, DPS, Heal) you could essentially allow all options to be available and limit them based on a set pool of resource... be it xp unlocks, research, loot drops, etc. You can't learn everything at once but you can have access to it when you want it.
I am with you on making everything avilable. Just need a way to limit things from bleeding over too much when combining. You want that stuff to be exciting and cool but we have all seen when two things collide unforseen effects can ruin gameplay.