I loved 3ds max back in the day, haven’t used it much lately, but there was a way to render a sky dome inside it if I remember correctly. Anyway what I was thinking is use hdri maps and skydomes at the same time. Kinda like parallax scrolling the way that old school sidescroller’s used to work put the skydome with mountains and stuff way back then put like statues the Eifel tower ect on the hdri map. I was thinking that if you had level one on one hdri map and level 2 on a second hdri texture that you could use a third map with a linear gradient to blend the transition between levels while the tiny landscape and the level geometry stream into memory. Just a thought. Hope it helps.
Maybe have like a world level then an auto slicer that exports it into the level streaming system.
I remember back in ue3 and I never got around to figuring out if you coudl or couldn’t use kismet streaming and distance streaming together, but if you could that would be awesome for a persistent world. Have the enemies loaded up into kismet streaming then distance stream the world. That way you could have different sequences of events happen at different points in time. Like maybe at location 1 at level on you fight something like a band of goblins but then at level ten if you walk back through that area you get chased by a band of river trolls or whatever. I just remember walking around wow and it was cool but the world felt like once you used it game over move on to the next map.