Still, the strangest are the ones that mount CASE for Gauss and Plasma ammo, and the rest of the ammo was either on the wrong side or energy-based.
Well, CASE for Gauss ammo may be for the gun if it is in the corresponding arm. The Gauss explosion damage might transfer to center torso, so minimizing engine damage is good idea (even worse, head damage if torsos are badly damaged).
It is also possible that the CASE exists in case the Gauss rifle needs to be replaced with conventional ballistic weapon in the field. Might be overplanning, but then again salvage and field customization are time honored traditions within BattleTech.
As for plasma ammo, the only plasma designs with CASE that i remember are field-refits. Eg CPLT-C6, which is a field refit made from C5s, by pulling the Arrow IV and slapping a couple of Plasma rifles there. Do remember that CASE requires factory-level refit, but Arrow IV to PRs isn't.
So, it is there for sake of fluff. I approve such things, even if it leads "nonsense".