Actually, there was a start-up a while back which developed a system for just that --- parameterizing house designs completely so that end-users could customize designs to their heart's content. If you look up "Flood Editor" it should take you to information on it.

Interestingly, the company founded by the guy who developed the nailing plate which arguably made McMansions possible was an early investor in CAD, spending ~$1 million for one of the first systems.