Make it so the Guild of Lessors only accepts your prestigious stuff if you are a citizen of the Peerage Ward.
Why would a Ponds PC want to get prestige there or why would Rowan let them?
Seems like an oversight to me.
From my point of view, a Pondsfolk can also try to gather the good will of the Peers by donating items. They can then use this goodwill to bribe other Peers. So I don't think it's a bad thing...