I've dealt with this one on and off over the years, I have three boys and they all have this problem from time to time, like you don't want to give them treats for staying in bed nor will I lock the doors. and with three if they each wake up once a night that means I'm up three times a night, so I do understand what lack of sleep is like! my 7 yr old gets up the most in the night, and this summer has been hard, but here is what I find... and it is not that different from your previous advice,
I have to get his energy out during the day!!! make sure he doesn't go to bed hungry, I always make him go potty before bed. when he does get up I take him straight back to bed with as little interaction as possible, sometimes he has a bad dream (which I think is because of eating to close to bed time) if he has a bad dream we often pray to give comfort then straight to bed. we have had a bed on the floor before and sometimes he still does this on his own, it didn't make the problem worse, but it did give me more sleep, so I do recommend this as an option, just explain to him that if he does come in he can not wake you or Daddy up but he can sleep on the floor in your room, but he will need to bring his own pillow and blanket, I prefer to make it harder for them rather than make the bed for them or it is to easy if it involves an effort on their part they might think twice about having to drag bedding in with them, (my kids had a smaller blanket that they could drag in easily). but it did require work on their part, and it wasn't a very comfortable bed either, if they want comfort they have to stay in their bed.
before bed time I discuss the importance of staying in your bed... just because you wake up doesn't mean you cant go back to sleep without telling me about it, just go back to sleep, if you are sick then that is a good reason to come tell mommy or daddy... that kind of thing, no threats here, just honest conversation, which really does help in our house.
All three of my kids keep water bottles by their beds, the no spill kind so they can get a drink of water and go potty during the night without waking me up, which I also encourage them to do that and try to go back to sleep on their own before they wake me up.
best of luck, if you need more encouragement please feel free to contact me