As promised here is a before and after of the trick I described yesterday. This is just a quick test to prove that it works, but the results are obvious. As you can see the cheeks are stretching just as planned.
I call this method Low Weight Compensation. It is a simple solution to a daunting problem when animating characters for a limited system (namely games that don't allow the use of blendshapes). Basically, this method allows you to create the stretchy fleshy movement of skin without using blend shapes. It can also be done at a very low joint cost.
That antenna joint is acting as a sort of flesh magnet. All you need to do is move the joint out a great distance (I believe in this case it moves to a value just under 800 in either direction) then paint weights to it at very low values... say 0.00something. The further the joint has to move to get it to get the faces to stretch to the right position, the less the weights you painted will interfere with weights you already had. This is especially important in the face, because the weights on facial controls are typically more delicate than anything else on the body.
This idea can be expanded upon to make it more efficient in your rig. Theoretically you could even automate the fleshy movement by using dynamics in Maya though that could make things tricky if you need to make a looped animation. You really only need one joint for each area you want to stretch, in most cases you could probably do it multiple times on the same rig to get a more realistic stretch; it's a very open method with few limitations.