Some detail on what Elon Musk is proposing. I like the idea of landing directly on the launch mount and attaching a new payload while the stage is refueling. It’s sporty. If they’re serious about this architecture, it suggests that some of SpaceX’s near-future developments will involve a different sort of launch mount/hold-down scheme that facilitates this idea of landing a returning stage directly on the mount, rapid checkout/turnaround of returning stages (without moving them from their landing spot), and a means of rapidly integrating payloads to boosters at the pad (something that DARPA FALCON and ALASA have worked on, albeit at a significantly smaller scale).
But it strikes me that they’d be better off in the near term to simply have a second booster ready to move to the pad with the refueling vehicle. Sure, it’s got a gee-wiz factor to land directly on the launch mount, refuel and restack, and launch again, but I don’t see how developing all of that special-purpose technology could compare economically with simply building a second reusable booster.