Some instructors, who prefer a BP&W for their own use, don't like to teach OW students in them, because some students can't get out and back in them in the water.
Er, there is little easier to get into or out of than a "Hog" rig.
1) Open the waist belt buckle, if the crotch strap is properly designed the waist belt will fall away and the buckle will slide through the loop in the crotch strap.
2) Reach over and grab the tank valve and pull the entire unit over your head. The unit ends up tank valve towards the diver plate up
To don:
1) Position the unit in front of the diver as above.
2) adjust harness straps and hoses as required
3) Slide arms under harness, and flip it over your head.
If done at the surface add sufficient gas to wing keep rig afloat, and the diver sort of slides under the rig, no lifting required.
Add a 7ft primary hose and a bit of planning is required to avoid getting tangled, but it's not hard to master.
Picture the "Studs" that like to flip their bc over their heads in the parking lot, only in the water the gear is weightless.
Tobin