Was it Serpent that tried bracing via the engine mount somehow?, though I think they now run a normal brace in the latest rear revision?.

I'm fairly sure someone else tried no brace, then the brace came out shortly after, and it looks very tacked on...

Really I'm not going to judge what Mugen do at all, just anything to do with design I find interesting, overall I think the CAD images are great to look over, other point for me is the engine position looks kind of odd, or more so offset more than the old MTX4.