This is a big, fat, slow expensive unit that the vast majority of the time is just a sniper artillery piece on tracks.
C3M does not benefit this unit at all, although it is also a big expensive lump of tech and I can see the temptation to put it well out of harms way I think putting it on a slow, poorly armed crawler might be a false economy
Guardian ECM offers little so far away from the battlefield - and is pretty expensive
The 2xLPPC do offer a slight discouragement to tanks and asf looking for an easy kill but they're not going to discourage much.
Personally I would be much more inclined to split this vehicle into 3,
a 50T tracked FCE could move 5/8 and carry a Sniper and 30 rounds - speed being a great strategic asset for getting the gun where it's needed or away from threats
a similar mid weight, 5/8, tank as an escort - an off the shelf myrmidon would do just fine giving a PPC and also an SRM for dealing with infantry (infernos)
Fit the C3M in an on field support element like an LRM boat that can actually benefit from it. It will also make it much harder for an enemy ECM unit to get between Master and Slave