Aluminum tank? Go to steel and lose about 6# with no other penalty.
FWIW, you simply have to figure out what specific part of the kit is contributing to your buoyancy, then see if you are willing to deal with the expense and trouble of switching. Like, going from a Ranger > Back Plate/Wing likely won't do squat for buoyancy. Redistributes the weight, more stable tank, trimmer, carries weight better, etc, but not likely do much for improving actual weight required unless the Ranger is adding some float.
Sounds like that's a full 6mm thickness 'standard' density neoprene? I had a 6mm standard neoprene Bare suit I borrowed for a couple months when my shell was in the shop getting new boots. It fit very well. I was excited since I thought the neoprene would provide insulation comparable to my original 7mm wet-suit AND be DRY!
What I found was the warmth was decent to ~60', then the neoprene got so compressed I got cold, just like the wet suit. I had to add back ALL the insulation I used with my shell suit. FWIW, I'm small and skinny, and prone to being cold.
I also found the bouncy swings was actually worse than the shell. Not only did I have the dry suit bubble, but I had to deal with the compression swings of the neoprene. I ended up not being terribly impressed. Happy to get my old shell back. It wasn't warmer, but is was less to deal with.
THEN, a few years later my wife and I went to a top of the line/custom 5mm COMPRESSED neoprene Seasoft. We had both been using shells for years. Over the first half dozen dives we gradually dropped 6#, AND increased out bottom time ~10-15", with no penalty in being cold. The suit was that much better. There has been a move away from neoprene to shells in the community. Damned if I know why. They simply are not as warm as a GOOD/COMPRESSED neoprene suit using GOOD neoprene. Be aware, there are LOTS of grades of neoprene and you generally will have a hell of a time finding out that specific info from the manufacturer or retailer.
To Air is Human,
To Respire, Divine.