I like resistance bands a lot, but the heavier they get, the bigger, and to get any granularity in your resistance choices, they can eventually wind up taking up a lot of space. The flexibility in their use, if you're a creative thinker on how to use your body, is unparalleled, though. The big ones can even be used with handles for deadlifts!
I'm not sure how to describe what might be an even better alternative, but there are canvas strap apparatuses that you can hook onto something and use like a pulley system with your own body weight. You can hook them on/loop them around trees, or to the top of your door, or a car bumper, etc, and do a virtually unlimited set of exercises with a piece of equipment that compresses into just a bag. If you have a sufficiently strong roof support(I've seen some build these into their vans on videos), you can even hang them from inside your van and begin to do things like pull-ups, etc. The TRX system is a well-known one, and I got one that was a cheaper brand but no longer available. You can use these to stretch, too. If you want something lightweight, flexible, and that goes into a small container, I don't think you can do better than that sort of equipment. There are usually courses and such on how to use that sort of thing best, but like with stretch bands, there's almost no limit to what you can do if you can use your body sensibly and creatively, everything from endurance and stretching to HIIT.