I can never consider FC House as House since it is made more for a base of operations for FCs.

A good design for a FC House would be more towards designing the FC House to be a bar rather than a house.

Small House, as shown, is only the size of a Inn room so not much can be done but to turn a Small FC house into a place like a cafe.

Medium House size makes it possible for a much larger bar for the FC base.

Mansions are shown to have two rooms on the 2nd floor. While the bottom floor can be designed to be a bar the top floors can be design with 1 room being a meeting room for FC members and the second room can be designed as a Office for the FC Leader and officers.