[_Microft]

Since PCB manufacturing has become super cheap, they could consider having a custom L- or U-shaped custom PCB around the battery box that serves no other purpose than routing signals and power to where they are needed and solder the different boards directly onto that. That would also allow to place supports for this large PCB where they are convenient instead of having to separately mount each of these small PCBs to the case.

With less cables in the way, they might get better airflow in the case as well.

Edit: I guesstimated the size and think that they could get five pieces of such a board for less than 20€, including delivery.