Expensive, but oh so lovely. Independence Weaponry learned all the right lessons when they laid this beast out.
The NG-C3A model is the first (and IMHO the best). Built as a pure fire support platform it is all long range weapons, triple Artemis equipped LRM-15 racks, six tons of ammo (pull from the LT bins first to extend the life of the C3Master), and a dead flat heat curve with a standing alpha strike. Not only do the guns have excellent reach, but they have a short range of seven hexes, perfect for the spotter to stand just outside an ECM bubble and still give the best targeting data possible to the Naginata.
What doesn't get mentioned is that it is a standard fusion engine design, and both torso are CASED. True, an ammo cookoff in the left hand bins will take the C3Master with it, but the mech is damn hard to put down completely. The weapons fit the job perfectly, stand off at range with a clear field of fire and bring the rain of pain, augmented by your lance or company net feeding you targeting data. Pick priority targets and concentrate fire till they are at least crippled. Fast movers with high firepower and ECM carrying units are top of the list.
There are two other variants, not really the best IMHO. The C3B is a company command design that strips one of the LRM racks for a second C3 Master, an ECM suite, and a couple ER lasers. The C3C drop the Master and a couple tons of ammo for a C3 slave and jump jets.
I can see the theory, but 2 C3Ms in the same machine invite a decap strike, and while the common parts are nice, jump jets are a bit of a luxury on a firesupport machine. I'd rather have two C3As, rather than a C3B and C3C in the command lance.
While an excellent command mech to anchor a C3 lance or company, as Cold1 points out when building the formation how the rest of your C3 net will work with a Naginata is a vital consideration. You will need at least one (up to three in a full company) fast movers to get out early to spot for you, and probably a few mid range brawlers to be to deploy as a defensive line against attempts to slip a jammer, backstabber, or assassin back to your Master and firesupport machines. Building a C3 formation is like cooking, the right spices in the right proportions will enhance the meal. Get the balance wrong, or throw anything in there just because you have it and you've produced inedible slop.