I have for many years used elastic bands.  They sell them as crossfit bands.  I tied a rope around one end, the rope goes around a tree etc. and then I pull on them.  You can do most upper body exercises as well as many lower body exercises, including many that cannot be practically done with weights.  I use two black bands, I think 80 pound resistance, and two red ones, I think 35 pounds.  An improvement over this system would be some kind of box with a spring in it that gave a more constant resistance over the length of the pull, and mimicked the maximum acceleration that weights have.  Not what you seem to have in mind, but it would be way better than any machine.  There are lots of machines and they are too expensive and not very good.

Chest presses or push ups for your pectorals and crunches/sit-ups for your abdominals would be worthy additions.

But the cyclist in me cries out, "Don't forget your legs!"

Speaking of which, used inner tubes make good resistance bands. It's funny, I was just thinking about how these are differently nonlinear than gravity and weights are, and then I started thinking about the feasibility of doing curls while on the ceiling by using resistance bands attached to the ceiling...

This incoherent deluge of thought was likely sparked by throwing out some inner tubes and reading a book in which the main character lived in zero gravity and had a centrifuge for exercise to keep himself healthy.

Thanks for the response.

I alternate every 6 months upper/lower, and during the summer I hike a *lot*. Like, sometimes 40 or more miles of hiking some weeks in the summer. Legs shouldn't be a problem.

Normally, adding cardio would be also required since you can build muscles without the cv needed to support the strength, but I'm pretty good with cardio already so that shouldn't be a problem either. I might throw in a 3 mile run (on a traditional machine) with each session just to be sure.

Lat pull downs and rows would be good additions in my opinion.