I wouldn't worry about mog house. Its already made...just need them to unlock it.

MH = Inn near adventure guild. You even enter at gridania's MH during r30 GS quest (and they are very similar to FFXI MH in style).

I believe they're holding it because actually MH, AH and DB were near the same structure. Maybe they're holding this a bit for some reason since AH is also already made (Limsa near docks). I believe that, at correct timing, all three will be released at same time.