I would run a short battery never in a 4wd sedan. In an off-road car or a F1 they are fine, but the weight penalty is a small price to pay for the amount of power they give up after a minute or so if the amp draw is sizable.
I'm all about getting the weight down to the class minimum, but even I won't use a shorty in a sedan.
There's probably 40-50 grams to be saved in the driveline with the new lightweight parts. If you dump the gear diffs for a spool and a ball diff, it's another 25. I'd look another place to pinch grams.