There have been mixed feelings on the slow take off with the addition of pw gears. Some say that can't notice others say they can. I think that noob or someone posted some good numbers talking to the percentage of gain by changing the gear ratio. Search around for those or he might have them on hand.
Some guys mounted another swing arm on the other side of the wheel and put another spare qt shock on that side. You can replace the single shock on the qt, but what you need to look out for is a shock that has an a-frame linkage. Needs to have eyelit top and a-frame bottom. But that isn't necessary if you can fab up a new bottom linkage that would allow you to go eyelit to eyelit. Noobster made a shock extension that might work. Another thing to think about when replacing is that the shock is close the wheel and a new shock might rub or worse.