Enix, I don't think the aliens need a counterpart to the support kit. The idea behind it is that it just allows humans to survive more easily outside their base, and as it provides its wielder with no means of self-defense, a support man's teammates would compensate for their extra ammo and health by having to actively defend him. Plus, assuming we make it cost a lot of money, if a support does get killed it means a lot of cash down the drain. And finally, adding a support kit won't have as drastic an effect as adding a new weapon; you're not going to see packs of support guys prowling through hallways like you might in the case of a new weapon ("OH SNAP XAEL GANGBANG"). On a medium-size game, you might have one or two on your entire team.
This would, of course, have to be playtested to be proven. It might just turn out to be an unfair advantage after all, but seeing the ways that I think it could improve the game, I do think we'd want to add a counterpart to the aliens instead of botching the idea.
So. As for your shield alien, Enix, I'm not sure I see that working out. Almost the entire alien team has its own unique style of movement; how will the shielder be able to cope with all of them, and stay in front of them all to shield them? Especially since with the different alien speeds, they won't stay together enough for a shielder to cover more than one or two aliens at a time. In fact, the only aliens that commonly travel together by species are rants and dretches; rants are too big for you to effectively shield more than one at a time, and dretches (the good ones, at least) wallwalk so much and so unpredictably that a shielder would be rendered mostly useless, even if it's big enough to shield a whole pack of dretches if they were clustered in one place.
Secondly, and most obviously, more than one humans automatically negate the presence of a shielder. It's called circling. :P
And the final and most important problem with your alien is that the alien team doesn't really need a support class at all. They're designed to fare well on their own anywhere on the map, and all of their abilities and stats regenerate automatically, save for poison (and a poison-giving alien would be going too far, in my opinion). If that weren't enough, rants also have their healing aura, and alien forward bases are often much more viable than human ones.
So what the aliens might need instead (if indeed they need anything new) is a new non-support class, somehow. Hey, maybe we could make Battle Granger an official alien class? :D Idea I just thought of: one of his abilities could be eating grenades to stop them from exploding. First, when a gren is thrown near him, he would be visually/aurally alerted to it (it might glow in his field of vision, or produce some ambient sound, or both), then he'd go up to it, hold one of his attack buttons for a set amount of time (two seconds or so), and then just gulp it down. When it explodes inside of him, it could make a muffled "Boom!" sound, and a little puff of smoke would come out of his mouth. Tell me that wouldn't be adorable.
Another idea that came to me right after typing that: perhaps, if you could make his class sneaky enough (temporary invisibility?), he could in addition to/instead of swallowing the gren, just pick it up with his mouth and carry it for several seconds, to move it out of the path of danger or, more importantly, INTO the path of his foes. As a matter of fact, I think this is a pretty good idea. Even if it doesn't need to be used as a counterpoint to a support kit, this could perhaps be part of another mod.
tl;dr: Nix on the shield alien, and thumbs up on a battle granger.
