Wrapperup tried to do this and many other people did to but they just quit on it because scripts to load the terrain are deleted.
wrapperup and those other people are using static shapes to load in .dts shapes and make 'interiors' out of them. this process is p simple; it's just about making it user-friendly and modder-friendly.
terrain will not come back in its original form because there's not really an object class you can manipulate to make infinite terrain anymore. you could theoretically create terrains with static shapes, but i'm p sure the collision capabilities are limited and so it'd be kinda goofy to get it working well (and looking good)
[end implied opinion, begin explicit opinion]
in the end, bricks are still superior and we should be focusing more on making building easier than trying to bring back deprecated functionality and trying to grab onto a lost cause. we need actual tools to create maps with bricks [efficiently], not necessarily even in-game. this would be bigger and more powerful than some jerry-rigged static shape machine or a hacky re-implementation of dead classes.