Paradox, I think a lot of those ideas would be better implemented into unique aliens/weapons/armour than as upgrades purchasable by anyone. For example, acid trail could be a good adv basi ability, exept you trigger it with mouse2 and it lasts for 3 seconds with a 6 second cooldown. The acid could do mild damage, and slow down human walking speed by 50%. THAT would make the adv basi more worthwhile.
And the morphing could be an s3 adv dretch. When immobile, you inherit the texture of the surface you're attached to, however for balance reasons you still stay visible on radar. For humans, the rifle could hold 40 bullets per clip or something similar.
The human morphing could be a cloak pack, an expensive pack item that makes the user invisible (but not on radar) for 30 seconds when activated. 60 second cooldown after activation, and you become visible when firing or when taking damage.
Others:
- an alien that always deals poison damage
- perhaps an alien that can drop acid charges. the charges take 10 seconds to grow, during which time even 1 damage will destroy them, afterwards they detonate when a human is in sight and range. The alien could only field one charge at a time.
The ones I didn't mention are, imo, either very OP or would just serve to confuse people. When I slash a battlesuit in the head as a Tyrant, I want to be sure the second shot is going to kill him, and that he isn't packing an extra 15 hp. Likewise, I wouldn't want to attack a dretch just to find out he now does 140 per headshot.