Backwards PLT.
My point was simply that as it stands there is no longer a GR4 replacement and when that (very loyal, long serving) war horse is put out to grass then nothing is going to back fill it. This is because the money was spent in the 'let's go to the C' decision in SDSR.
So there is no GR4 replacement.
But JCA (not repeat not JSF) can help fill the GR4 replacement criteria if we buy the C. It cannot if we buy the B.
So if you want to 'have DPOC' or 'replace GR4' (same difference) you have to do one of two things. Either accept that there are no extra frames but the new ones will cover up some of what you can no longer have - buy the C. Or you can argue for a reversion to the B to meet the JCA requirement and ask for your money back - buy DPOC.