Yeah, all of those would be good improvements, but the downfall is, is that servers that WANT those tiles to block (to prevent access to areas they dont want players to be in, and still make it look nice), would have to go in and change a lot of tiling, or their servers would have some minor problems
If there was something in a predefined section that could make the tiles choppable, pickable, or walkable, and place it as some kind of NPC automatically, that would be awsome...but there isnt