Please do consider the other systems that are not already subjected to the same (external) heating and pressure during launch. There is the plumbing, for instance. Even the engines depend upon some amount of cooling during launch, which they don’t get during reentry. The Merlins and Raptors would have had to have been designed with these extra problems in mind. Even Rocket Lab’s engine compartment would have been designed with these considerations. The engines, fuel tank dome, and other items may be a bit heavier than they could have been otherwise, but reusability always required tradeoffs that one-and-done didn’t need. Probably a reason why many engineers believed that reusability was impractical.

“I wonder if even the barge could be eliminated by landing on a convenient island?”

Although this sounds good, the reality is a bit different. The flights generally do not go in the direction of islands. Most will fly due east, some seem to be going south (where there may be some islands available, maybe), and ISS missions go toward the north.

Return by barge, from an island landing, is the most likely method, as airplanes are usually only cost effective in delivering payloads to the launch site in a timely manner. Equipment returning from the launch site generally takes the slow but cheap routes, as time is no longer of the essence.

Sorry about your dream of seeing an AN-225 carrying a Falcon booster. That would have been a good sight and picture.

Of course, the next logical step was to eliminate the “reverse the booster’s trajectory” part, by stationing a landing pad at sea along the path the booster would take anyway, were it being thrown away like everyone else’s are! Barges are a lot easier to build than rockets!

I wonder if even the barge could be eliminated by landing on a convenient island? Bermuda? Someplace in the Windward chain? How to get it back? An AN-225 might do it, or just plug in a nosecone and fly it back?

I do think it is an interesting coincidence that the Falcon 9 and the Electron rockets share a similar engine arrangement, with 9 engines in the 1st stage, and one vacuum optimized engine in the 2nd stage! So it’s no surprise the burn time for the first stages are also similar, 152 seconds for the Electron and 180 seconds for the Falcon 9 (according to Spaceflight101 website).

That burn time for the Falcon 9 may be a little deceiving, since any recovery of the first stage requires eating into the burn time by a significant margin.