Great idea! I always wondered why they didn't do this with the Falcon 9 rockets. Since the super heavy booster is so big and expensive, they could save some money by testing a small-scale version using the Falcon 9 rockets.





Using the grid fins as landing legs looks a bit awkward, since it offers only four contact points with whatever apparatus is used to capture it. Also, if the rocket drifts due to cross-winds or imprecise control it could hit the tower and do a lot of damage. The design needs to be damage tolerant, easy & cheap to repair/replace parts. Aircraft carriers use cables to snare a tail-hook on fighter jets when they land. Cables are damage tolerant, cheap, and easy to replace when they break. Also, expensive hydraulics aren't needed, since a simple winder and brake is sufficient to pay out and slow it down the cable. To capture the super heavy booster, you could use a cable-based snare. One version puts the "hook" on the rocket, and a snare on the tower. However, in my opinion, this is still very similar to what is described in the video linked above. My preferred design, would have the cable on the rocket, perhaps joining the tips of the grid fins together, creating a large spider web of cables at the top of the rocket. These would snag a hook(s) on the tower, mounted to a long counter-weighted & guy-wired crane arm. The hook could be designed like a treble-hook, hanging loose and dangling from a cable. All cables could be on winders and use brakes to absorb impact. This design would capture the rocket like a fishing rod catches a fish.

And I don't have a billion dollars to build my own rockets, so I offer this idea freely.