Looks like a solid concept. Make sure to doublecheck battery thickness vs. vertical space in the chassis, it's easy to miss by just a hair and have it mess with the whole internal layout.
I'd also suggest once you get the parts, cut out thin cardboard mock ups of the armor to do a final fit test before you cut metal. It's also not totally obvious how the armor fastens together while allowing battery removal, so that's something to think about while the parts are on the way.
