I don't think they could. It doesn't really look anything like E-Megs in any form. I think it works in part because SG Megatron really isn't as iconic as SG fans think he is (and they seem to not be happy with it), and that SG Megatron is basically Marvel Megatron colors. So shifting him to a G1 body, it accidentally looks more natural than the new SG Optimus does.
I don't think even Galvatron could work for an update of E-Megatron. While E-Megs is a Galvatron homage, he's a really unique design.
As time goes, I find myself wishing that they had used Siege Leader Optimus for SG Optimus.
This is the weirdest combination of lazy+clever I have ever seen. I'm impressed. They gave us a convincing sci-fi jet without actually changing anything.
Yep, I both hate this and love it. It's tempting because it's so very close to Marvel colours Megatron, but I think I'm going to be strong and not add to my costs for the year. Because given how much they're milking this mold there *must* be a proper Marvel colours version showing up at some point. There MUST!