I'd forget about trying to duplicate the feel of your BP with a standard BC, I don't think it's possible. Instead, maybe consider why you're using a standard BC, and I would guess the reason has something to do with comfort and extra buoyancy at the surface, convenience for demonstrating to students, etc. If that's the case, I think you're looking for a regular jacket style BC. You could modify it, maybe take out the stupid cummerbund, simplify the harness if possible.
I'm thinking about this same thing for my DM course next summer. I'm dragging along my old SP standard BC, only I was able to completely remove the cummerbund and replace it with a standard web belt. I'm even threading a few weights right on the belt. I'm also removing padding on the shoulder straps wherever I can. So I should have a set up that works really well for assisting with OW classes in which you spend alot of time at the surface helping out the students, and is somewhat less annoying to actually dive with.
