If your skills are "that" good you won't be shooting a 870.
or at least not an 870 that hasn't been heavily altered by a competent shotgun-smith.
You can dump a bunch of money on stocks and rails and lights and such, which is fine. It's your gun, your money and only you really know what you want.
But it sounds to me that you are trying to force your 870 express into being something it just isn't.
I have to take you at your word that you can handle your shotgun, that your skills exceed just knowing how to load, point/ aim and squeeze the trigger and hit your target.
Given your physical limitations (don't know if that's the best term for it, but bones grinding in the wrist would certainly limit me), I can only suggest a different, new shotgun, customized to best fit you.
I have serious doubts that any off the shelf aftermarket parts are going to help your situation. You seem like you need a custom fitted stock, custom balanced gun, that fits you like a second skin. You're not going to get that with an 870 express, at least not without spending much more than the gun cost to begin with.
If it were just a matter of "I like to customize my gun cuz it l00ks kewl" then I wouldn't have even bothered to comment.
The "options out there" you mentioned in post #57 are off the shelf, mass produced aftermarket items. What you need is a craftsman who can build you a stock, balanced, weighted, and fitted to you and you alone. That level of quality and craftsmanship can't be bought off the shelf, not even a nice Boyd's is going to get you there. And if you do go this route, I'd want to upgrade over an 870 express. Lipstick on pigs comes to mind. A nice vintage Wingmaster, maybe.