Even then, I think Magnus gave them more to work with. I can see things working out for Megatron, though, as ball joints and universal joints could be made to work in that space.
The Seekers idk much about, but I remember being very surprised getting back into the fandom (never having seen most of the original toys) and discovering that the FISTS were add-ons. Probably doable to have them flip out of the fuselage or something (or stay in so the slip-on fists can be used instead). Maybe have the wings on a bracket so they can be raised up to be above the shoulders instead of at the waist. But this may be stepping a bit away from the original.
I'm just hoping they hew closer to the Sunstreaker end of the design spectrum than the Ironhide. Keep the jank and just add a bit of range of motion.