I don't see why getting rid of the terrain/interiors is a bad thing.
Yes, I know TDM's can be huge on game terrains, but do they look good?
Perhaps switching to slate could make people actually taking time to build stuff, instead of making two forts against the Pacific and calling it a fort war. This will force people to make what this game was purposed for; build. Either way, I'm quite certain that people will, sooner or later, will create advanced terrain generation mods, till then there's LSG and TerraGen, which, I admit, aren't really subjects to use. But who knows.
I personally like, and even enjoy the idea of getting rid of terrains/interiors.
One thing I admit that will also break due to the removal of terrains is skis. They will be almost purposeless considering they also bug the forget up, alike with vehicles, on the bricks.
While playing with the base of the game, it's often known that implementing something can break another.
The engine update from v9 broke Add-Ons, for instance. But in time people began to ignore that and accept the fact that the new update will open new borders.
As Kompressor said, removing terrain and interiors will mean that optimization will be less of a hassle and there can be more concentration on making a more feasible physics system for vehicles, so they still have goddamn purpose or content. Or God Badspot knows what. Perhaps a integrated land generator? Well guess not.
Anyway, in conclusion, I fully support the Shadows and Shaders due to the above.
..Or just because I build just on Slate/Plate...
I just thought of something that would be awesome.
Due to the new shaders, will ENBSeries be compatible with Blockland now?