If I was to start a feather like that:

For drive, 2 drillmotors of 9,6V to 12V, I would put 2 NiMh racing packs of 7,2V around the 2000mAh to 2400mAh mark in series so you would get 14.4V. It is easier to find good inexpensive chargers for 7.2V racing packs than it is for 1 14.4V pack.

Add these to a Scorpion (X)XL or a Sabretooth controller, and attach those very nice blue wheels that James Cooper sells and your ready to go.