Tileset
 

I like the concept behind the tileset 1 type that lets you place things into blocks, but I'd love it could be taken a step farther and I could define blocking tiles MYSELF whether by script or what.

I would love if I could just have a tree image, put it where I want, and be able to assign the tiles a block or dontblock myself.

And I would love if the original tileset structure would allow me to place competent buildings into the tileset so it makes sense.

you can, if you make your own movement system. [onwall/onwall2]

quite possible although somewhat burdensome.