I work at a mid-market CBS affiliate notorious for penny-pinching, and that's the damndest thing I've ever heard of. That's old-school thinkin'!
I presume your current graphics move when you use the AE RAM Preview trick. Here's what you're up against to do what you want:
You'd have to prepare a totally-separate set of gray-scale animations: white is totally opaque, black is totally transparent, to use as a matte for the color graphics.
You'd need the gray-scale animations on a second computer, running a second instance of AE.
You'd have to be able do your previews -- on two computers -- with absolute frame-accurate precision. That's the real challenge.
Your switcher would have to be capable of accepting one source for Fill and one source for Key.
I think it's time to bite the bullet and get a CG that's capable of doing that stuff. If you get the right one, you can put your AE animations in it.
Besides, now that there's Creative Cloud you can get Premiere Pro along with AE, and you wouldn't need a CG.
I've never used this plugin, and its now discontinued, but if you are on an older version of AE, this may work for you.
It looks like they are basically giving it away free for anyone who is interested in using it in older versions of AE, so might be worth trying one way or another.