I think the market ward system is fine, BUT, I still stand by my assertion that the wards should be enlarged, should require retainers to be in a stall in order to cap how many retainers are in a single ward (hence why they need to be enlarged first - I would recommend a design that allows for roughly 3x as many stalls as they currently have), and should force all the cities to be at least 75% full before spawning a new shard for that ward (Tinkerer's Ward 1, Tinkerer's Ward 2, etc).