gzt: Problems with the equity related proposal. You will immediately hit a problem when people want to use equity to finance their grownup kids into a house. Other than that maybe you're right it could reduce the kind of activity that every make a million in property seminar recommends. Assuming you want to exempt the kids scenario, I'd guess reliably knowing the difference could be challenging.
I don't think there should be any kind of exemption. If you own a house that cost say $220,000 in 1999 (thinking of my parents here) and it's now worth perhaps $1M, by virtue of inflation and the effort of the community (keeping the area nice) it's had a 500 percent increase. Being able to use existing equity has probably driven a lot of this, that's not to ignore a general shortage through population growth etc.
I still wonder how many people would own baches etc if they'd had to come up with 20% (or more for non-owner occupied) deposit in cash?

