Streaming map alongside original GTA V map?

Does anyone know if there’s a way to stream a map alongside the original GTA V map? Like, I don’t want to replace the GTA V map, I just want to add on to it.
The specific map I’d like is Akina. I want to have Akina be there, instead of replacing the entire rest of the map.
I have searched google up and down everywhere and have never found any tutorials or anything to do this.
All help is appreciated- thank you!

ymaps are able to do that, the conventional ways involve replacing the level, but ymaps just “add stuff” onto the level, including whole new islands.

@Blumlaut from what I’ve heard, YMap only supports objects and not terrain. The map I want has a bunch of terrain. Also, it is not a simple .xml file, it’s is rpf’s and such.

thats bullshit, ymap supports everything.

thats fine, look at the Akina mod on gta5-mods.com

yes, ymaps are naturally stored in rpf archives