Okay. Here's my concern:
Remembering that OP+ removes "obsolete" ships 2 years after the ship is refitted. The ISC's refit schedule:
2265, W-refit issued. Mandatory in 2267
2268, P-refit issued. Mandatory in 2270
2270, Y-refit issued. Mandatory in 2272
2279, Z-refit issued. Mandatory in 2281
There it is. The ISC's "locked" into picking PPD-equipped CAs as of 2270. The I-DNP doesn't come out till 2288 (shiplist year 25!) So, for the 18 year period 2270-2288, every ISC CA, BCH and DN carries a PPD. So, the ISC "line ship" deployment pattern for 18 years, in the upper TBPV ranges, is mandated by the 1 PPD rule to being DN / BCH / CA & 2xCLY/Z. Carrier groups are the only other option.
The "typical ISC outgunning" situation is a myth, based on perception alone. Consider these ships:
I-CAY, 165 BPV vs I-CAZ, 194.
I-CLY, 132 BPV vs I-CLZ, 151.
Now, consider the matchups. Tell me that the I-CAY outguns all the CAs of their era, when it can't even stand up to a BCH by BPV. Or the I-CLY is going to wax all the CAs it sees, when it's only as strong as say a D5 or NCL with medium drones.
Are the ISC still such "overbearing" opponents at these levels in these eras? What makes the PPD so fearsome that people are only willing to face ISC ships that resemble Gorn with a phaser-blind spot on the tail instead of the actual PPD-using ships of the ISC?