Your description makes the suit sound just like my tech instructor's Waterproof dry suit, but I know his is a D10. He said that lining wreaked total havoc with his buoyancy for a while after he got the suit. I really don't think I would like that.
Plus, as you say, back zip is lame. I have a Bare XCS2 Tech, which has the diagonal front zip. I like it a lot. It has never leaked (in 14 months or so). I can get in and out of it with no help at all. And I can take a whiz without even taking the top of the suit off, if I need to. It's crushed neoprene, so it is heavy. And is uncomfortably warm when the surface conditions are hot out.
Plus, as you say, back zip is lame. I have a Bare XCS2 Tech, which has the diagonal front zip. I like it a lot. It has never leaked (in 14 months or so). I can get in and out of it with no help at all. And I can take a whiz without even taking the top of the suit off, if I need to. It's crushed neoprene, so it is heavy. And is uncomfortably warm when the surface conditions are hot out.