Add the ability to add regular blocks via MTS, along with stair and slab variants if possible.

So, finally made up my mind. This is gonna be a wontdo due to how it fits into MTS's systems. There are other ways to get this, but it won't be in MTS.

Definable slipperiness? 👀

So, I'm not sure about this one. Purely because I'm not sure if it'll fit into the existing MTS systems well enough or will break them and be a PITA. I'm going to table this as a backburner until I'm sure about it.