Like you say, many of this exist already, but I can see the value of bringing it all together.
The problem is that many of these assets are hard to work with inside the editor, given that the editor was never designed for 2nd floor objects or objects that break the norm regarding placement.
If you take a look at the source of yuleland and the source for phitt's mines you can see the work involved of placing these correctly.
So I think we will also need to create a how-to manual that comes along with this
In Yuleland you will see that a wall that needs to be placed as a second level object can't be a door class since the collision detection is build into the engine and not the model. That means that a door far above you will still block your movement, that leaves you with decoration class with wall placement, and that's something you can only place on a wall (and there is no wall, since you want the party to walk under the object), so in order to bypass the "safety guards" in the editor you are placing the assets in different spots and then moving the with the WASD keys to the correct place. Needless to say this is a lot of work, and when you start to make more complex structures the worms really start to come out off the jar.
In the Northern Realm Project we are trying to bring into existence a town with NPC's, a place where you can walk from outdoor to indoor seamlessly and all these tricks are being used to the max.
My editor looks like data corruption on steroids and not a level design tool, its hard for me to keep track of all the assets placed over assets that are placed over yet more assets, and I made this so I can only imagine what somebody else will think
Sometimes I wish for a button inside the editor that says "Turn of placement restrictions on assets" so I can just place what ever where ever (hint hint AH

)
All my time is going into creating assets for the LotNR project so this something I will not be taking on at this time, but if somebody wants to bring all these assets together in a pack he can take whatever I created from the packs on the nexus.
Skuggasveinn.