Lightbulb!
How about creating a spending option that directly benefits other (non-family specific) players in some way?
For a rough example, maybe give a rich family the capability to build a recruitment center (or some other infrastructure) in a realm/region with their family wealth that others can use? Kinda like how rich families will fund stuff (albeit usually for tax breaks) in the modern world?
Give it similar coding to the current recruitment center page, but change the numbers (both make it more expensive and possibly better chances to get better units) around so a rich family actually has a reason to use it instead of just using the existing page.
Or maybe allow rich families to put on a Tournament run by the family rather than a realm; to make it easier to use, it could even bypass tournament grounds (at significant cost)... After all, I'm sure a rich enough family could make a temporary tourney ground pretty easily with enough gold. In addition, a tournament in your honor is a perfect way to flaunt your gold and it gets redistributed to other players.
(I can make these into formal FRs if there's interest in either option.)
