Unfortunately such a tax would be limited by prop 13 in California.

While the proposals here can be implemented on a local level, any change to prop 13 would be a state level ballot proposition.

(For the record, I'd love to see reform of prop 13. While I love the idea of smoothing out over a number of years the impact of sudden inflation or increases in local housing prices on existing residents, it should be a smoothing rather than an entitlement for long term owners of multi-million dollar homes to avoid property taxes.)