I really like your idea of fitting an upper half over the batteries! Makes me think of chopping off the top half of the Maybach that John Goode made for me. I own a hacksaw, but will this mar the paint?
Guys.
I fitted a full engine bay plus resin engine to my Tiger (see my gallery), To do this i had to relocate the batteries under the turret. This has the advantage of putting most of the weight at the center of gravity and thus avoiding the rear suspension collapsing over time.
If you go this route take care to ensure that you leave room for the turret rotation motor and note that you will have to modify the gun elevation motor mount to give some clearance.
Finally there is no room for a blank firer.
Hope this is of help
Steve