I'm not sure if this is possible, but essentially what I'd like to do is create portal doorways to simulate transporting the player to different biomes in the world, using level streaming with sub-levels to allow me to build out different biomes in different in-game time zones and respective visuals for deserts, forests, mountains etc, something like in this concept picture:

My first thought was to use a level streaming volume when you hit the area in the doorway, but you can't see what the portal is going to stream once you hit the volume from outside of the volume, so the doorway would be blank up until you went through it. I tried expanding the volume outside the doorway bounds but then the sub-level streamed in on top of the sub-level I was in, which is no good. I had a thought to use a scene capture component projecting onto a render texture on a plane in the doorway, with the capture component being moved around the same space as the player camera's position relative to the doorway, which is what you would do if you were just teleporting the player to another location in the same persistent level, but then I'd have to figure out how to get the scene capture to only render stuff in the sub-level, and as far as I know there's no proper way to do that short of editing engine code, which is outside my skill level. The only other thing that I can think to do is to set up a huge-*** connected world with the biomes being sectioned off into sub-levels that are streamed in and out, but then that becomes an issue of restricting the sub-levels in terms of pathing and layout so that they're properly loaded in and out, which is something I'd like to avoid if possible, as it'll just jack up my design time and also prevent the portal setup from simulating the time of day differences on each respective side of the portal.

Anyone have any ideas?