Just one thing to think about, I used to use a battery box and it was a royal PITA, I think the box was installed before the console so it was a real struggle to remove the battery due to the space between the lip of the battery box side and the bottom of the console shelf - so I had to do some thought about what options worked for me and I couldn't find anything off the shelf, so i had something made.
This is what happened to my battery box when I tried to remove the battery's the first time...
I got the batterys out but the box was a total mess, so I had to cut it down, I made a bit of a try with an upright side to support the externally mounted battery switch and ran with this for some time, and it worked well with the batterys strapped inside - meaning I could lift the batterys out the side for charging at home or checking the connections.
I didn't like the idea of the open top, and not having any side protection for the batterys so I drew up some drawings, and had a new larger box made, giving some extra space for cables, and also so I could internally mount the battery switch so this was had better protection as well.
My idea was similar to the old cut down box, with a tray and one upright side left for the battery switch, then a U shaped bit to slide over and then finally a lid to cover the top.
The box is made of marine stainless - I know this sounds like a recipe for potential disaster, but the inside of the box is lined with high density foam, and under that lined with a heavy duty rubber insulation, and each battery is independently strapped down - The batterys have more support now than they did in the old box.
Due to the removable side, removable top and cable entry holes the box is not air tight - so no issues with venting.