Gyroscope= keeps you heading in the same direction, even when wind or outside forces try to alter your course (hooks to the steering servo basically) without you touching the the steering wheel.
I would keep the Ti skids in place, they will be a life safer should something unexpected happen and you slam into a wall at max throttle.
As for the body, the Proline slipstream gets my vote as one of the most aerodynamic shells for an MT, otherwise a truggy shell of some description + big ass rear wing.
A pair of 6s lipos wouldnt be that heavy, got to remember that one typical 2-3s lipo pack ways half that of a 6 cell nimh pack, and I've seen guys running 18 of those cells in dual BL maxxes back in the day.
As for your tranny issue, you can always get this great chap to custom make you the required output gear in aluminum, to fully beef it up:
http://www.rc-monster.com/forum/showthread.php?t=21856
Mod 1 pinions from Mike go upto
25teeth, beyond that KershawDesigns sell Acetyl plastic pinions with a brass insert upto 38teeth, though I would rather get something from
SPD-SI custom made then use a plastic one.