I remember clearly that Yoshi answered exactly this question in second from last live letter and only Largge size house / plot will be capable of having the workshop (I've mentioned it as well in the Big-House-Price-Thread). As mainly crafter I was planing from the very begining to get only large house for my micro-FC (less than 10 members) but after publishing the prices in the patch notes I can forget about EVER having the FC workshop (((