Older puppy won’t sleep through the night

We’ve had our almost 6 month old husky/shepherd mix since he was 12 weeks old. Since the first couple of weeks, he’s always woken up between 3-4 am and cries to go out, where he usually pees and poop. It’s as much habit now, I think, as a genuine need to go. He goes out for the last time around 10, and we are usually up around 6. After going out, he goes back in his pen. Sometimes he falls right back asleep, sometimes we have to sit with him for a while to get him to re settle. Any suggestions for getting him to sleep through the night? He sleeps in a playpen in our living room (he failed crate training hard, very stressed being constrained). If we ignore the whining it escalates to barking and then a full tantrum.