Nonnef's come up with a rotating arm that can be fitted to MP Ratchet & Ironhide that swings the hip kibble round the back. But... it needs surgery to insert. Very tempting though if it's unscrew/insert/rescrew. I've done that enough times. I would like to see a video review.
I believe PE likes to use diecast in accessories (because ZOMG DYCAAAST IS SO GEEWUN EVERYTING WITOUT SUX!), so if that's the case here then it'll be even harder to find a legend (indeed even a titan) that could support it.
Indeed. For all the practical and sensible "make X new toy look more like the G1 version", the thing that fills me with joy about the TF community on Shapeways is that every so often you get a properly, gloriously bonkers idea.