My A700 and Evo 2 both come in at around 1300 grams RTR so I am already having to add 50 grams of ballast, lightening drivetrain parts would be counter-productive for me.
I would like to see a stronger version of P11, seems that they wear out and eventually slip over the pin which causes slop in that diff pinion area, and can bind up the whole assembly. Seen it on a couple of cars myself. Maybe an alloy tube? Most cars which have bearing spacers in the hubs use an alloy one.