Refitting to the Keyhole-II standard
The entire Keyhole concept is based on the mass management of large numbers of missiles through remotely deployed platforms which are themselves extremely large. The entire electronics fit of the Keyhole I-capable ships is significantly different from that of any pre-Keyhole ship. Major changes in the internal electronics of the ships would be required to incorporate any sort of Keyhole capability. Moreover, the platforms themselves are larger than people seem to be assuming. These are big suckers, Richard. These aren't deployed from boat bays; they are deployed from specifically designed and fitted broadside bays, and they are substantially bigger than any Ghost Rider drone currently in use. In fact, they are closing in on the size of a LAC, and they are actually larger than some of the LACs which have been built. What all of this comes down to is that in order to refit Keyhole II to a ship which wasn't already designed to have it, you have to pretty much gut the tactical section, rebuild it from the deck sole up, and simultaneously figure out where the ship is going to carry, dock, maintain, deploy, and beam power to the Keyhole platforms themselves. That's why we have one of the characters -- I think it was Hamish -- referring to the fact that they can refit Keyhole II only to "late-build" Alliance SD(P)s (that is, the ships which were built after Keyhole I was incorporated into their plants). The Andermani ships which are deployed to Eighth Fleet were new-build units which had been altered on the ways to incorporate Keyhole I. The "six-week" refit time which Hamish quoted for them was for the time required to take a ship which already had Keyhole I and replace the first-generation platforms with second generation platforms. It was most definitely not how long it would take to refit either Keyhole capability to a ship which had never had it in the first place. Note that the ships coming to Honor at Eighth Fleet are substantially delayed from the originally projected delivery dates for "refitted" Andermani SD(P)s. That's because they were never part of the "refitted" program at all; those ships went to Home Fleet, Zanzibar, Alizon, etc. the Andermani units [sent] to Honor were part of the modified new-build program, which then wound up being refitted because BuWeaps had managed to get Keyhole II to a deployable state after all.
You can, indeed, if you wish refit the grav-pulse system even to a pre-pod superdreadnought if you really wanted to. I'd estimate, however, that the time requirement to install this system aboard any ship (pod-layers or pre-pod) from scratch would be a minimum of four to six months. Since the Battle of Manticore takes place just over a year after the beginning chapters of the novel, the ships which were going to be available within the next 18 months are just over the horizon from deployment. Personally, I can't see Manticore diverting resources from their new construction projects to refit pre-pod ships, or even existing pod-layers, with their new-build ships that close to completion. Besides, simply figuring out how they were going to man the old-style ships they captured from the Havenites would be a logistical nightmare, following the losses they suffered in the Battle of Manticore. Not to mention all of the problems they'd have with nonstandard spare parts, people not familiar with the internal systems, and all of the other "Not Built Here" problems which would attach to the Havenite prizes. Eventually, they certainly will take all of their own existing SD(P)s in hand and refit them to Apollo standards, but at the moment they desperately need every surviving ship they have deployed to cover themselves against the possibility of a Havenite follow-up attack and the unresolved tensions with the Solarian League. Besides, throwing that many ships into the "refit" queue would seriously disrupt their construction programs by diverting desperately needed components (and yard space, yard capacity, and yard workers) to the refit program. It makes more sense from almost every perspective to get the new ships built, commissioned, and manned while using the old SD(P)s (any of which is at least as capable as anything Haven has left) to cover their vulnerable areas. Of course, what do I know about it? I'm only the author. [G]