rstofer
Contributor
The Zeagle feels very similar to a BP/W from what I here, and the extra padding makes for a very comfortable hike with all your gear on. I am not sure if a BP/W would offer you the same level of comfort and support, please feel free to correct me if I am wrong though.
OMS makes harnesses that are indistinguishable from high end BCD setups. See Fig. #5 here: OMS Technical Dive Harness Backplate Systems http://www.OMSdive.com Ditchable weights are a separate issue.
I suspect that those who dive with a minimalist harness have no desire to bring along the extra bulk.
Richard