I was actually thinking of doing something very similar. I tend to lean back in every chair I sit in, and after a couple of years, they always break. I've broken several chairs in the past few years in nearly the same way. I'm not fat, I just constantly lean back and occasionally prop my feet up which puts stress on the joint that connects the base of the chair to the stand. Eventually it either wears out or in one particularly hilarious case of epic chair failure, just shears through the metal sending me flying backwards; both nearly killing me and destroying my computer.
I like the idea of a monitor on a swiveling arm that's attached to the wall or the ceiling; very future-techy. Since you seem like the hand-man kind of man (and it's an old chair) you should also try and build some kind folding table attached to the chair for your keyboard/mouse, like the ones you see in college lecture rooms that you pull up and the over your lap. You'll probably need to go wireless for both the keyboard and mouse, and should therefore build a "holster" for them when it is in chair-mode and not desk-mode.
If you want to go all out and become my new idol, you might as well build a chair-puter. It would require some serious work, but the more I think about it, the more I want to do it. You could position the computer within the chair, or in a holster on the side of it, mount the swivel arm for the monitor to the chair, and if you REALLY want to make me and every other human being on earth jealous run wires from the motherboard to a custom made control panel in the arm of the chair so you can turn the thing on without having to bend over and push the button on the case.
The more I think about it, the more I think this could be the most awesome project ever...
I don't think I'd ever leave the chair...
I'm very interested to see what other people say about this...
BTW, if you do make something truly epic please at least PM me with some pictures so I can envy you forever lol.