Actually, designing our own powers ingame sounds like fun.
Three areas to choose from: Tech, Biotic, Passives, with melee being available through all three.
Each level up gives you points you can then use to build your powers.
You pick what kind of power you want to build. Powers come in many shapes and forms: Thrown powers like Warp, instant hit powers like Reave, self powers like Barrier and so on. AoE? Cone AoE? Jumping from target to target?
Next step is deciding what kind of effect it should have. Dmg to health/armor/shields/barriers, crowd control effects, AoE radius etc. Does it prime? Does it detonate? Both?
Passives contain things like power dmg, weapon dmg, health, shields and so on.
You can upgrade those powers you made, increase their damage, range, radius, add secondary effects
That way we can remove classes completely and we are no longer limited to binary evolutions. The only limit would be the seperation of biotic and tech, cause I can see way too much potential for abuse there. Energy Drain Singularity that explodes into a Flare and self detonates biotic explosions after stripping all shields, just as an example. :>