Okay...
As an experienced ISC captain (though not a ladder player), Looking things over, this is what I've seen so far...
On the rules site:
PPD Deployment Limits: The ISC limited the fielding of PPD?s. For a Squadron of ISC ships of 3 or less, the number of PPD?s cannot exceed 4. ex. A CCZ and CAZ together have 4 PPD?s, so their 3rd ship could not have a PPD. A DNZ alone has 4 PPD?s, so none of it?s wings could have a PPD.
Just to let you know, typical PPD deployments in the ISC fleet as of the P refit on:
I-CS series, light cruiser, 2 PPDs
I-CM series, light cruiser, 1 PPD
I-CA series, heavy cruiser, 1 PPD
I-CC series, heavy battlecruiser, 2 PPDs
I-DN(H) 4 PPDs
I-DNT 2 PPDs
I-DNL 3 PPDs
I-BB 4 PPDs
"Strike" Carriers typically have PPDs (usually 2), while the "Fleet" carriers typically have Plasma, but won't be an issue as, IIRC, carriers require 2 escorts, and no ISC escort carries a PPD. The newer "oddball" ships work differently, Fast cruiser and Local Defense ships have no PPDs, while the NCS gets 2 PPDs on a CA-hull...
So, a CCZ / CAZ pair only has 3 PPDs, allowing a CMZ / CAY as the 4th PPD.
It takes either a DN / BB, CC / NCS, or CC / CS combination, to prevent a fleet from having 3 PPD-armed ships.
Oh, from the sounds of it:
That is almost exactly how the PBR PPD Deployment Restriction is worded - except our in house SFB Rule's lawyers interpreted the rule as saying the 3rd ship allotted an additional PPD 'slot'. I actually initially interpreted your way.
And the current PPD rule is derived from the initial reading...
Because if you went with the "group's" interpretation, you could go DNH / DDZ - FFZ / CAZ for 595 (w/DDZ) or 573 (w/FFW) with 4 PPDs on the DNH (or DNZ to save 14 more BPV) and the 3rd ship (CAZ in this case) triggers the "additional PPD slot", making a 5-PPD fleet...
I noticed the rules page called for all fights to occur in "late" era. Exactly what year is this, as it determines a couple of choices available to the ISC officers... From what I remember of Firesoul's design, refits "overlap" for like 2 years. 2279-2281 is the best range for ISC officers to work in. The reason being is that the "Z" refit is issued in 2279, and "Y" refits are still available till 2281. Being that the "Z" refit adds anywhere from 10 to 29 BPV to a ship, it can mean the difference between CCZ / CAZ / CAY (588 BPV) or CCZ / CAZ / CMZ (577 BPV) as a top-end "DN"-centered fleet. CCZ / CAZ / CAZ is not possible in your rules because the combination is 617 BPV, and you've capped the BPV at 600...
One other thing, I'd recommend making the full PF tenders fall under the "Carrier" rules, since Taldren, in their infinite wisdom, prevented the PF races from fielding true carriers, calling the PFs their "fighters" instead. Also, I think, at least on a Plasma standpoint, that this would help even-off a "carrier" battle, as it's PF-tender w/ 2 Pl-D escorts vs. Carrier w/2 typically AMD escorts. Otherwise, it gets very tempting for the PF players to grab a tender with 4xPFLs as their "support" ship...