What would your special unit be able to do?

[Bulby37]

I think the vortex as it was described would be OP and take away the fun. Take off the damage component, or limit the pull to one unit. The tactical advantage of moving your opponent's planned attack or defense line to a position they did not see fit to put them into in the first place should be enough for a skilled player, no need to add a sniper/runner/medic nuke into that equation.
A lot of these ideas remind me of Starcraft. I would have to say that invisibility is not an utterly terrible idea, so long as it was done in the same fashion as an arbiter, with a telltale unit pretty much telegraphing the existence of cloaked units, but not revealing the number of units, what type, etc. could also be used to feint a cloaked attack and draw the enemy to a certain area to discover there are no units actually cloaked within, just in time for all your bases are belong to dust.
Also, a ranged AoE hit point buff machine (a force field or shield generator) might make an interesting counter to bombshells.