This is my only issue with the market wards, and will only become bigger as more people play the game. It was a decent concept but the limitations make it only viable within a certain small scope. It's made worse by the fact that the wards aren't linked, though that would only be a temporary fix at best. As much as I hate to say it, the wards are a doomed system. The only way they could keep wards as they are without this issue would be to remove the designations on what things go in what wards, add more wards and link all of the city's wards together. There would still be a cap on how many retainers could be present but it would be much higher. And of course despite removing the labels on the wards, keep the search system as is or better.