Bloss - exactly the same problem here with my 4yo DS!
I'd like to know what or who he's dreaming of
Like your DS he is also in such a deep sleep it is often impossible to get him to do a wee. This is made worse by his insistence that he will not sit down to wee - must be standing up and of course he is so groggy he just staggers around or his legs buckle under him!
We put him back into nappies for a while - just wasn't worth making him feel like he as failing. At his insistence we tried again recently and he was better and managed to stay dry for the first couple of nights but then lost it again. We're back in nappies again for now with the promise to him that we'll try again in a few weeks time. He just gets sooo crestfallen when he has wet the bed that it doesn't seem fair to him to keep going if he's really not ready for it.
I'm not sure whether it is related but the rising boys book does say that they get an adrenalin surge at this age. I'm hoping in a while things will settle down and lifting him will be easier.