I second Pazyryk comment and/or third Verdian's. And Folket's
I'd rather see, for example, Houses discount some unit/building types, or just give much lower boni. I don't think the number of new units or buildings is a problem - that's fine - just the total benefits a House brings.
Maybe require more work from the player to get all the benefits? Consistently feed a House's desire for conquest, trade, or whatever. So maybe at lower support levels you get some benefits, but you need to be at a high level to get the full benefit. And a high support level decay's faster than a lower level.