So steel plate with additional 6 lbs, so total 12lbs all on your kit.I would be in my steel plate and either a HP100 and about 6 lbs total or in an al80 with 10lbs in pockets on the waist band.
Don't get me wrong, not getting separated from your gear with a lot of weight can be a challenge, which is why it's nice to practice it. Doff over the head and keep it close to the body and there aren't any problems. Or take it off jacket style, but have the diver spin into and out of it but that is easier to do when vertical rather than horizontal.
I do think that this should be taught in open water, but would you agree that for cold water divers with 20 lbs or more of lead, it is more risky?
I think instructor control has to be on point and not sure how many would be up to the task.