Here's a fix:
Okay, you got your cool looking Grimlock in hand, but you hate that dumb transformation/ jaw gimmick that looks horrible with and without the mace attached and is reaaaaally obvious


But do not despair:
If you take this hinged big chunk of plastic and twist it up-

You get this:

Which IMHO, is insanely better looking
Now, pros and cons.
Pros
You get this vaguely...I don't know, back...ruffle? Either way, in person it looks great

I seriously cleans up the robot mode

And when you peg his mace in with this tweak... (Make sure it's backwards, the main body of the mace should be on the Dinosaur mode's throat)

AND THE BEST PART IS......It centers the figure's center of gravity and, dispite the weight of the gimmick, makes him WAAAAY less backheavy.
Now the cons:
You really have to force it into being upright, it sounds really bad and crack-y, but my figure has done this several times and hasn't resulted in any stress marks or breakage
Secondly, you do get a bit of kibble behind his head

Now, I've not found a better way to arrange that piece directly behind his head, but I can deal with it, plus it make's him a bit bulkier looking IMO