This is the issue that people have currently with multi-owning things and I don't see your suggestion fixing that problem, especially if now that option will be locked behind a paywall and not something that anyone can do with a couple of alt characters on a single account. It will directly benefit spenders/whales while leaving people who can't afford to spend on anything besides their subscription in the dust.
The issue also becomes more extreme if they integrate the workshop into these instanced houses, at that point it's just: "how big is your wallet?" in terms of how much gil you can make and makes the process easier for those who sell gil/who wish to sell gil to generate it.
