Terrain on runtime

I searched around the forums and I saw it is not possible but the latest thread I saw was from a couple releases back so I dont know if anything changed or if it is planned to change…

What I want to do is grab heightmaps from the internet and create terrain from them on runtime to massively reduce the size of my project. If its not possible outside the box is it possible to do so by to tweaking the source? I know programming but never tried to mess with source files before.

If there are other people working on it on github or something id love to follow along or help however I can.