It looks like a novel system for infantry support, but the potential to put so many warheads into a given target in one turn if you flush full cassette-loads from all four trailers in a complex... don't get me wrong, I'm sufficiently steeped in RL military lore to be a colossal fan of 'one-salvo kills' (witness my 'Hailstorm' system in the Virginia War AU), but an alpha-strike from a CMS can throw more than a hundred missiles at a single target. I think the system needs a little more detail before I can determine how balanced it is:
...It gets worse. The 'Unique Technology' segment has a Point-C3 system, something that links two vehicles target/tracking system together but offers only a +2 to-hit (it does nothing to affect range modifiers like the canon C3 system). All of a sudden, you have 8 trailers, with a +2 firing at you.
If you check the rules, a tow vehicle controls ALL its trailers - imagine somebody using a munchie 50-ton 7/11 tow vehicle...
[shudder] Self-emplacing fields of up to eight claymore mines with range-brackets of [-] 7/14/21 each? I'd hate to be the
light 'Mech pilot who thought he could bully infantry in
that neighbourhood....
- Once a cassette is expended, how long does it take to dismount the empty and load a fresh one? IMO, reload time could be the key factor in whether this system's balanced or outright broken. 
Found the reload time on a re-read; I'm a little worried that a single turn is too fast, but see also the next point.
...I had thought 30-seconds to a minute - but how many turns is that? I keep meaning to check, but I can't find it.
As
Dread Moores has pointed out, you'd want to make the delay 3-6 turns to match the BT assumption of ten seconds per turn.
If you wanted to complicate things, you could base the reload time on the number of crewmen attending each launcher; slightly more simply, maybe you could make it a simple dice-roll? Maybe reloading a CMS launcher requires the crew to hit a given TN on 2d6; after one turn, they start rolling, needing to make a TN 12 in the second turn, 10-12 on the third, 8-12 in the fourth, and so on. It reflects variable degrees of crew-training and the inevitable 'friction of battle' known as Murphy. Brilliant/lucky/skilled crews might pull off a reload in twenty seconds, while ham-handed rookies might take over a minute. (And if a crew hasn't reloaded by the eighth turn of trying, they're probably dead already anyway!
)
- The system is described as a five-ton trailer: how much armour does it have, on each facing and its 'turret'? 
- The 'Cable Check' table - is that for any hit, or just ones reaching the 'damage threshold' mentioned above the table? Because according to the entries on the table, hits that can knock out a trailer's connections have a statistical likelihood of only 2 in 216 (1/216 each for power and data cables)....
...ooooh, you're gonna hate this... There is only a single ton of armor, in a 'clamshell', protecting the hydraulic post (and nothing else when its moving). The trailer is butt-ass naked. If it's hit - >boom<. Its only when its emplaced (normally in an 'Improved Position'), that it has 8 points of armor protecting it from fire in the forward arc; it has none from the rear, or overhead. It has no turret location
Actually, that's a
relief. If these things could actually absorb punishment, I'd run screaming, but making them 'soap-bubbles armed with sledgehammers' that die if you breathe on them means they're far more frail than I'd assumed; as you noted in the system's description, a good bombardment with artillery (or a few cluster-bombs from your supporting ASF Stars) will go a
long way to neutralising these systems, and that sort of 'ready antidote' seriously cuts down the munch-factor.
1 in 216! Ok - that's a bit much. Maybe, "Roll 2d6, on a twelve, loose the cable for the rest of the game."
1/36 - the same odds as a Gauss-rifle headcap, or a jam knocking out an Ultra-AC for the duration of a scenario - is much better from a balance PoV.
How long can those cables be, by the way? How much separation can the control-vehicle have from its launchers? And how do you track where the cable-runs are, for the purposes of hit- and damage-resolution? My first instinct if I knew I'd be facing these things would be to blanket any possible control-vehicles with artillery airburst fragmentation-rounds, in the expectation/hope that the shrapnel would cut a large number of cables and neutralise much of an entrenched launcher-complex before it could engage.
