Maybe we could team up with the Freedom Ship (yet to be build) and MS The World (ResidenSea) in this project. See Seasteading on what we can work together on. Although MS The World more looks like an 'eternal vacation for the lucky few' who just want to evade taxes (at least that's my feeling),instead of really be focussed on creating new possibilities and technologies.
As for the transformation of oil-platforms into cities,we should also go underwater. We could build the underwater parts around the foundations/pilars of the oil-platform,reaching to the seafloor and even go underneath that.
These Walking Cities (Freedom Ship a.o.) could use the Seasteading-Cities as harbor/port and refueling/transfering hub,as well could navies and coastguards use the cities.