I do think that, since A1 receptors directly inhibit CB1 receptors in the hippocampus, and upregulation of A1 means more of the receptor. Now if you want a deeper explanation than that... I don't think you're going to get one lol. I don't think they know that much about why those CB1 receptors work the way they do yet, but I do believe that they're critical in sleep. I've actually read studies showing that anandamide, one of the big endocannabinoids, induces REM chronically without any tolerance or withdrawal, and that definitely seems to fit with dreaming to me.

You may be able to get lucid frequently even with drinking caffeine every day, but... well, consider the fact that I can get lucid frequently with smoking weed every day. That's a pretty well-known REM destroyer. Just because you're able to overcome your self-inflicted handicap doesn't mean you wouldn't do even better without it. I'm willing to bet that it would be even easier for you to become lucid if you cut out that caffeine consumption.