Ah! Kirkhill, where to start to dash your hopes again?
Lets put it this way: I love dreamer but:
1) these small phibs are not repeat not "combatants" in the sense of the CSC. They could not fight their way out of a paper bag if their life depended on it.
2) You cannot just "stretch" a CSC and put a "flat deck" on them so they would remain the same ships. They would be, by necessity entirely different: different internal arrangement of machinery, different internal compartments arrangements, different distribution of equipment and on-board services, different ballasting and tanking arrangements, and likely even a different hull form would be required, etc, etc. So, if you want small phibs (and I would personally like to see phibs in our Navy) it is a lot faster and smarter to start either from scratch or from a foreign design we buy than try to start from a CSC.
3) The San Giorgio's are not bigger than the envisaged CSC's - in fact they are about the same size but shorter.
4) The San Giorgio's have a limited lift capability: They can only carry about 400 armed personal for landing and about 30-34 large army vehicles. They do not repeat not have the capacity to embark either the task force commander or the Admiral and their staff. No on board medical facility to talk of either.
5) The San Giorgio's have a very limited capacity for helicopters: there is no Hangar to store them in (they stay on deck, with the afferent corrosion problems from exposure to salty sea air) and especially when the LCVP's davits are in the upper position, limited spots and embark capacity of maybe four or five medium helicopters at most.
5) The CSC are extremely unlikely to be able to ever land the CH-147 Chinooks: The CSC's and their flight decks are small and the Chinooks don't have a haul down system, making the sea states in which you could safely land them on a CSC quite limited.
As I have said, I would love for the Navy to have phibs, but my choice would be to acquire something more suited to our needs, with about the same size crew, but that would provide good helicopter capacity, better troop transportation and heavy equipment capacity, actual room for command staffs and good medical facilities. For about the same price as the San Giorgio's, these would be Mistral class ships, or if we wished to go a little bigger and a bit pricier, the Canberra class.