That's not a new idea. When I joined Battlemaster, most of the realms I played in flat our decreed that all gold belonged to the realm, and the only difference was what degree of freedom you had in spending it to further realm goals. Of course, that was under the old tax system when it was easier for Bankers to force that.
I'd say the lords should then band together and tell the rest of the realm to !@#$ off. After all, they have the gold.