I will freely admit I am new to the WorldWorks product line, but have loved what I've seen so far.  The only shortcoming I've found is the lack of open door and window models.

Open doors are important for a lot of game pertinent reasons, especially regarding stealth or horror games.  Telling the player to picture that the door is open is kind of defeating the idea of using a 3-d model set in the first place.

Open windows are not nearly as important but would be nice to round out the options.

The only other thing I'd like to see would be two story tall tavern walls so I could build a double level tavern complete with balcony.  I know I could clip the regular walls together, but it isn't as stable.

Yeah, duopble story walls, not especially tavern (its hard to play under the balcony) but more Dungeon und cave walls, because with multilevel caves, things like the (C&K)twostory bookshelfs and so on I like to build high walls.
Its impractical to have a real balcony to play under, but with the raisers you could make multilevel rooms.
But often the walls are then to low.

You could just cut the doors and windows and score them lightly at the "hinge".  You could then open and close it.  Doesn't seem like there's any special to do than that.  ;)

Yip...
To strengthen the hinges, you can use a small bit of clear sellotape...

I'd suggest you take a look at Himmelveil Harbormaster as a way to put together multi-story buildings. InteriorWorks could easily be built in a similar manner.

Castleworks Ultimate as well.

I do this with most of my buildings, works fine. As a cheat (and one that I have only recently started doing) you can glue a strip of paper on the inside of the fold on the walls that the door goes, reinforcing not only the hinge, but the door itself.

The Auld Grump