Someone may have asked this already, but why not use some kind of system similar to "mobile" oil rigs? The kind that float into place, partially submerge, then tether to the sea floor? Seems like the best of both worlds to me...

[edit]...It could also serve as the launching platform. In this way the launch/recovery pad could be floated to the rocket, boarded and built, moved into position near the equator, then launch and recover.