Ooooh~! Idea~! Do you think something like a sort of reverse rocket launcher would be possible? You know how explosives blow up terrain? Well, what about a gun where you put in a tile you want(uses said tile as ammo or condense the explosive radius in number of tiles displaced and craft them into a singular 'rocket') and it basically explodes INTO whatever that tile you selected was. If it would be too much, could always make it work for only dirt, stone, maybe a couple other blocks, etc. Essentially, a way to quickly fill areas with blocks for big building projects, filling with sand, dirt, stone, etc.
Could end up being like rope in how that if rope wouldn't fit in that space, it won't spawn, and maybe it drops the 'wasted' blocks from the created rocket! Sounds like a weird and complex idea, but basically TL;DR: Sand Gun but better and not meant to be an actual weapon.