Of course not, I wouldn't expect you to ever acknowledge ...
Oh, I acknowledge that you could only do the described dive backmounted.
I couldn't! I would simply sit on the bench trying to get up without even moving an inch until someone took the tanks off me again.
You could only get me into the water with that amount of weight with a crane (and that would be a lot easier sidemounted).
To be able to drive in that area I would have to (e.g.) rent a zodiak, have it drop a line with the tanks and gear up in the water or spare myself the useless effort of trying. An alternative would be DevonDiver's rebreather concept, but I could never afford that.
I can only carry a comparable amount of gas in a sidemount config and will fail when I try to add the first or second stage to a backmounted setup while not in the water.
In my opinion someone who is able to do what you described backmounted, will also be able to do the same sidemounted, but with a different combination of tanks perhaps.
---------- Post added November 22nd, 2014 at 11:50 AM ----------
One idea for such a dive in sidemount is the 'floating clipline':
You use a clipline connected to a closed SMB and drop it with the tanks after the diver has moved a few feet away.
He will gear up in a few feet of depth, but strong current will sweep him and his tanks away at first anyway.
Another option would be the 'dead wale approach'.
Gear up lying down and have the crew roll you over the side