the problem with GA bulks (or any bulks) is that you are stuck with traxxas diffs, or need the uber expensive UE ultra lite diff cases to run 1/8 gears. With brushless power you will NEED better diffs.
it sucks about the layout, almost as if it wasn't made for electric!
The top plate only serves to hold servos and stiffen the chassis. You could eliminate it and make chassis braces to replace it. (think 1/8 buggy)
Or, if making a new top plate, I would place the battery box first and integrate the box and top plate to make one unit.
Also, if making parts, you could turn the servo sideways for a little more room.
Or, just run it like it is and tell all us internet bloaks to shove off!