People do seem to experience cannabis intoxication in a variety of subjective ways so I'm not ruling out the possibility that someone such as yourself could catch a dissociative experience from it. Personally I find weed to heighten pre-existing sensations/awareness and bring me very much into the moment, often a little too much, unlike dissociatives where one's surroundings slip away. It is in this way that I find cannabinoids closest in nature to psychedelics. I'm one of those people who doesn't enjoy smoking more than a couple hits of weed at a time, and while I've enjoyed using JWH 018 and AM 2201 several times in general I found them to be way too potent. I don't doubt that someone could get effects beyond the usual scope of weed such as hallucinations if they dosed high enough on certain synthetics, but I found the general feeling and tone of them to be radically different than the effects brought on by deliriants in the datura family. Just one man's opinion though. About cannabinoids having some kind of activity on the opiate receptors, I don't know about that and I'll give you the benefit of the doubt, but I don't personally find cannabis or it's synthetic counterparts to in any way resemble the opiate high. I wish it did though, believe me.
I definitely get what you mean about it bringing you into the moment, now. It effects me very much that way as of late. I could also see how that would be an effect you get most often if you only smoke a couple hits at a time. At higher doses for me, and always when I first started smoking, the dissociation was very severe. Rare out-of-body experiences, intense time dilation, tunnel vision, total separation of my internal thoughts and external dialogue, deja vu feelings, that sensation where you feel yourself moving but it doesn't actually happen until a few seconds later... all that good stuff. Synthetics can give me some flanging vision as well. And CB1 receptors actually inhibit NMDA channels so I don't find this at all surprising. On the flip side, the receptors supposedly also increase communication between 5-HT2A and D2 and are spread abundantly throughout the visual cortex as are 5-HT2A which, as far as I'm concerned, can easily account for both emotional and sensory psychedelic effects. Lastly, cannabinoids actually do work opposite to acetylcholine in certain areas of the brain, i.e. they're anticholinergic (hence the short-term memory loss), which can of course cause delirium in high enough amounts.
If you don't like smoking more than a couple hits of weed at once I'm not surprised that you find JWH-018 and AM-2201 too potent lol. They're generally thought of as some pretty powerful synthetics. However, just as a suggestion, if you really like the psychedelic effects of weed you should try looking into JWH-250 if you ever have the chance. It's so far my favorite synthetic, I think there's something to be said about some CB1 selectivity (though as it's the only "selective" agent I've tried, I suppose it could also be that JWH-250 just happens to kick ass). Every one of my friends who tried it, including myself, got powerful psychedelic effects from it, including but not limited to patterns, faces forming in the trees and clouds, acid-like mindsets, and lots of dissociative effects as well, all with very little incidence of anxiety compared to something like JWH-018... neat stuff.
CB2 agonists have been shown to have their effects reversed by naloxone. I'm not sure about CB1 agonists, but CB1 receptors form heterodimers with mu-opioid receptors if I'm not mistaken and so likely positively modulate their effects. However, just how much narcotic activity it gets out of that I can't say. There is certainly some overlap though, but I wouldn't try replacing opioids with cannabinoids, except for maybe a really selective CB2 agent. I recently tried A-834,735 and it had a heavy body high for me, but I'm not a huge opioid user (they barely do anything to me, natural tolerance runs in the family) so I'm afraid I can't draw too many useful comparisons.
For me it used to cause dreamlike visions when I used to smoke the stuff as a kid. I would say yes it has depressant qualities but I could never fall asleep within an hour of smoking it, hinting that the increased brain activity can be related to stimulants. I agree not only that it is the widest ranged psychadelic drug, and push the point a step foreward by saying, in my opinion, it is the widest ranged psychoactive drug. I have found it to be impossible to predict the effects of the drug with any degree of certainty.
Interesting thread
^^ I definitely agree with this. Cannabinoids are just crazy, especially weed. I love it.

I miss those early days....