[Minor details]
From an electronics perspective, I would say that the worst thing about the board isn't the battery placement. The worst thing is the power distribution board placement. The wires poke straight out and will want to travel at least a 1/2" straight out the side of the PDB. In this diagram, it look like the Jaguars in between the CIMs may have some wiring clearance issues unless the electronics team uses 90 degree mounts, so you could push the Jags our a little further so long as they don't interfere with the chain runs. It's great for how compact it is, but it would be a nightmare if a wire ever has to be replaced.
Also, you have a cross beam right underneath the forward-placed CIMs. The 4 Jags in the front MUST have their wiring go underneath that cross beam for the board to be fully removable. The best way to do this is to probably just have the wires poke down underneath the board right out of the PDB, then travel up to the front, then come back up through a hole right next to the Jags. Not hard to do at all, tbh.
[/minor details]
Another option that should give you more room overall is to create 1/16" or 1/8" sheet metal L-brackets for the Jags to stand them up vertically. Your current setup is ideal for this since all of the Jags are paired in their placement, so they could be mounted vertically back-to-back.
I love the weight distribution of this chassis; as-is, it will turn on a dime even at max speed

. Great job!