Well, Ezekiel, that could be an option too, but there is just ALOT of gold floating around in the game, so the way big house idea would be a good idea too. I think it's a viable idea for gold sinkage imo, and could use some fleshing out.
It shouldn't have to be super complicated, show up at an NPC, they have some easy to understand menus to float around through, and in a sense bank some gold on them (non refundable ofc), and the amount of gold on that NPC basically gives you the "entitlement" to place a second house on the shard that you started giving money to, but only 1 extra house per account. It doesn't just automatically just give you a house in some nifty area that wasn't accessible before but rather like I said "entitlement" to do so. Possibly make it to when you hit a certain tier like 7x7 for instance, and you place that house, then it erases all credit previously donated to that npc, so if you wanted to upsize you'd have to start from 0 gold again, or the amount left over from placing a 7x7 is still used to go to the entitlement of a bigger 2nd home. Perhaps a "rent" method is needed, like you suggested, or some mishmashed combination of both, you pay for your entitlement to place a 2nd house, and need to pay it's upkeep based on the size (possibly a percentage of the entitlement to place that sized house or some other percentage like how much gold is kept on that account --- which could lead to people just storing gold on a different account and possibly just impossible to do in the first place hehe --- or something that we aren't thinking of already).
I hope they put some brain power into some of the recent ideas that have been creeping up on the boards lately, anything from new pictures to extra houses, all seems fitting for us! We've been keeping the game possible for them for a LONG time! So show us some love on something we're actually asking for! Sheesh gold check books were even mentioned. SOT books (didn't see anyone ask for those but those were nice!), awesome. Community collections were awesome when they were introduced, I think those need to get a revamp though, or some new goodies offered through them which could be whole other gold sink idea. So many juicy juicy ideas here, don't let them slip away ^ _^
Edited for spelling and sleep depravity!