There are divers that dive a plain harness, that is no BC bladder or wing.
This flys in the face of what seems to be the dominant practice of adding only enough air to the suit to prevent squeeze and using the BC for Buoyancy control. The disadvantages of doing it all with the drysuit are that the greater air cointent will move around the suit as you orient yourself in the water, this includes filling the feet and legs, setting you up foor a feet first ascent. Additionally the vent on a drysuit is much slower than a BC dump making an uncontrolled ascent much harder to arest.
I'm tempted to try it this fall but it will be at a very tame site.
It is done but is not the way to start.
Pete