The JP kits are sweet. Very, very well made. Those little rails can be positioned in any of those slots.
The only battery that you'd be able to fit in there was a butterfly lipo pack...and even then it'd be extremely tight. And, to charge it, you'd need to either remove the hanguard and or figure something out with the wiring. Some guys are willing to do that for a certain look.
You'd be better of rear-wiring your mechbox and using a crane stock.