So you want a rail system for the front end and for it to house a battery up in the front somewhere?
In that case what you're looking for is a "PEQ"/Battery Box, put your battery in there and hook it up to your motor and you're good to go.
As for the foregrip, I believe there are some that you can screw into the stock handguard but it'll probably be better/easier to go with the rail system + PEQ + foregrip.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE