I kinda like where your going with this. I might fall back on the idea that my reality exists only in my mind. And each to his own, thus we all see a separate reality...one effectively imagined by us, only for us individually. I would put each of us observers outside of reality... we create reality by observing it. To observe, one mist typically be separate from. By that thought "the sense of the world must lie outside the world" may relate to consciousness instead of grand ideas, scientific principles, or patterns noticed in the larger universe.

There is no way for us to step outside reality to observe it, so to me this is a meaningless observation.

If Wittgenstein meant by "no value" that there is no externally bestowed meaning or purpose, then, well ... duh. However you and I are free to assign value / meaning / purpose for ourselves, to whatever we please.

Imaginations aren’t really outside the system though. I don’t see how anything can exist outside the system if “the world” is everything that exists. Another semantics problem.