GXV-T's technical goals include the following improvements relative to today's armored fighting vehicles: Reduce vehicle size and weight by 50 percent
Reduce onboard crew needed to operate vehicle by 50 percent
Increase vehicle speed by 100 percent
Access 95 percent of terrain
Reduce signatures that enable adversaries to detect and engage vehicles
I don't think that reducing the crew by 50% is going to be a workable option. After all, the tank will still need the same amount of man-hours of maintenance, but with a crew of 2 it will take the crew twice as long to do all the maintenance required.
But reducing weight would be excellent for multiple reasons. That would let a vehicle be transported in more ways. If you could get an AFV down to 20 tons at full combat load, you'd be able to deliver it via C130. A 35-ton AFV will be able to traverse more ground, and has the potential for a higher speed.
I can't believe DARPA is trying to get AFVs that do 120+kph, but talk about having a huge tactical advantage!
And reducing the various signatures is also a great idea, but I'm not sure how much can be done. I mean, millimeter-wave radar is more like light than like longer-wave radars.
The GXV-T program provides the following four technical areas as examples where advanced technologies could be developed that would meet the program's objectives: Radically Enhanced Mobility – Ability to traverse diverse off-road terrain, including slopes and various elevations; advanced suspensions and novel track/wheel configurations; extreme speed; rapid omnidirectional movement changes in three dimensions
Survivability through Agility – Autonomously avoid incoming threats without harming occupants through technologies such as agile motion (dodging) and active repositioning of armor
Crew Augmentation – Improved physical and electronically assisted situational awareness for crew and passengers; semi-autonomous driver assistance and automation of key crew functions similar to capabilities found in modern commercial airplane cockpits
Signature Management – Reduction of detectable signatures, including visible, infrared (IR), acoustic and electromagnetic (EM)
"Active repositioning of armor?" I hope they mean "automatically aligning the turret to take the hit on the mantlet," because anything else implies something out of Transformers!
The enhanced awareness is a good one, I bet tankers would kill to have the setup David Drake described in the Slammer's tanks (basically a 32" bigscreen TV with cameras all over the vehicle). I'd thought about using a helicopter-style helmet-mounted display, but I think that a tanker's head gets rattled around too much on the move for those to work.
checks out some 10/15mm railroad tracks for wargaming.
Sold all my M113 models and got these M9s ! 
