I'm interested to see how the gold purchase system fleshes out eventually. That was one of the things I was most excited about before getting the game and hearing about the rule set. I like the concept of a currency that affects features. Seems like potential for some neat things there.
I have to think the current Iron Bank/button system is kind of a placeholder. Cashing in multipliers for a couple million points doesn't amount to much when you're looking to reach the billions. I find myself just hitting the button when draining.
What would be a better use? Maybe double current multipliers for a period of time before setting back to 1x. Or cash in for gold, provided the purchases improve. Advancing each house by a shot for every so many multipliers. Lowering the shots needed to complete a house battle.