The bulge in the nose will overhang the box.
It's like a partial porch roof over the space. Forget about chairs and other large items. I have 2 x 6 volt FCLAs on my tongue, and I can barely remove and install the lids on the battery boxes. I also have to remove the hard plastic cover on the propane tanks to remove the battery covers. In short, space is tight, and the batteries tuck under that overhang nicely...but not a large storage box.
Height is an issue. Many aluminum battery boxes have slide covers, and they are designed to drop into the battery support frames.
Also note that flip lid "tool" boxes need room for the lid to articulate. Their lids overhang the box by a significant amount so they are water-tight. All that overhang needs space to pivot without binding into the diamond plate on the front of your rig.
Start here to get some idea of what's available. https://torkliftcentral.com/powerarmor-max-a7710r
These are crazy expensive compared to truck bed tool boxes, but of course they are rated for batteries. They also provide good security for expensive batteries. Perhaps leave your LiFePo4s on the tongue.
Whatever fits in one of these can be as long as the box is wide, but it can't be wider than the box is deep or tall...the dimensions of a battery.
Another option would be a tongue mounted bike rack...I think some NoBos come with these. The rack could hold chairs and other large objects, and the new battery box could hold smaller detritus.