This is something that I certainly agree with and would love to see. In the short term we'll be providing APIs to position furniture and query the position of furniture, so making an addon that saves layouts locally will be possible. In the long term it would be really cool to have a system for trading house layouts on a grand scale.

This sounds great!

What's the max length of the body of an in game mail?

Also, some other things running through my head at the moment:

• API - consistent item location co-ordinates (maybe relative to the starting position when you enter the home from the main door - will there be more than one door?)
• API - consistent object order (for deliberate item overlap)
• API - ability to select group of objects, then use API to iterate that group using a relative point at the center of the group (center X,Y can also be done by code, so relative point not absolutely necessary)
• API - ability to place objects relative to a given point (to import a group), and possibly leave group selected (or make API call to select objects so we could place a bunch, then select them all)
• API - validation that an object is owned and can be placed (in case someone tries to import a friends house and doesn't currently own one or more objects)
• Designer - ability to select/manipulate group of objects

Sorry for the brain dump - hope at least one of these things was helpful :)