Huh? Selector problems? I've been MP5-ing for a while now and I haven't had any problems there.
Accuracy on MP5's is often marginal at best, because of the short barrel length- all the more reason to invest in a tightbore barrel, especially if you end up getting a low- or mid-grade gun like a JG. The SD6 variant is also good because it offers a longer barrel length.
My recommendations if you want to stick with one AEG for indoor and outdoor is to leave the FPS at around 340-350, and juice up the ROF. I have a tuned up mechbox and a Lipo battery- FPS isn't a big deal when you've got good accuracy and a wicked ROF.
Get AV'd and you'll find an AEG you're looking for on the classifieds or on ASC's retailer pages. Other than that, you'll be looking at modding the Aftermath Broxa or Lycaon.