So you mean you split your 3D world into sections (points), and depending on what section you are in, display a different cube map / sphere map? What would be different in each cube map? Would buildings appear closer / further depending on what point you are at? Is the player inside a city or on the outskirts of the city?
Half life 2 does a decent job at creating their 3D skybox. They have a low res and poly count 3D skybox which they render in addition to the original 3D scene which doesn't seem to be a massive issue. Depending on the distance the player is from the building in the 3D skybox, you could just increase/decrease the resolution of the buildings. I doubt rending a bunch of rectangular prisms (8 vertices, 6 faces) with a low resolution texture can be that graphically intensive when many modern games have player models with thousands of faces to render.
I would say that there are already elegant solutions to 3D skyboxs, so read up on a couple engines which use large worlds (maybe other 3D mmo games?).
Note that I am not that educated with 3D, but I am curious to how this would work compared to the typical methods.