I would say buy it, it's a great price.
Seems like a an early bladder, never saw that design before. It's a dual bladder, the longer hose is intended for ease in use of the integrated inflator/octo, if you plan on keeping the octo or similar octo, the hose is just right for that purpose, if planning on dumping the inflator/octo in favor of coventional inflator, I would shorten the hose to the standard 16".
The dump valve, it's up to you to dump it or not, I bought one for my rig when it came with an elbow.
Pockets it's a user choice, my DR weight pockets ride high and are used to store safety gear, but are accesible enough for me and I don't see how you can't reach them right in front of you.
The harness type is not my favorite, but should be very confy and last you for decades.
I can't coment on the tank setup, since it's not my expertise, but a used set of manifolded doubles retails for more than $200.00 for sure.
My only complaint would be the gargantuous bladder, if you don't need all that lift, even tightening the bungies may end up with a too big of a wing, but then again, if you need the 100# lift for slinging stages, the wing will do.