Let’s be clear, without joking I think you are wrong to dismiss these possibilities and that you have an almost pathological lack of imagination. Yes, science fiction is about techs that do not exist yet are plausible.

You can fit a pool and a greenhouse in 250t. 40 cubic meters of water is 40 tons, 40 cubic meters of soil is basically the same. You have room to spare for the tennis court.

I am not a pro aviator, but I am a pro engineer, on an unrelated field, but I can do my napkins calculations. I mentioned the An-225 to make a point on the physically possible payloads that are possible today, with proven tech. I am not proposing we need those neither do we need the exceptional specs of that exceptional plane.

We scale down speed, it scales down drag (and necessary thrust) quadratically. We assume better efficiency on solar panels, batteries and motors because that’s what we will have in the future. Needing thrust only for sustaining flight and not for take off is another x5 factor on your calculation.

you’d still need at least 40 000 - 150 000 m2

Look at you! You managed to scale down your initial super confident 600 000 m² estimate by an order of magnitude! I am proud of you!

but as a wild guesstimate, I’d say the an255 needs some 40 000 to 120 000 kW for sustained flight in fair weather.

From what I am reading this is about the amount of power an airliner uses at max power on all the engines. You are looking at 1/10th to 1/20th of that for sustained flight, and quadratically less at lower speeds that those typical of those airliners.