To the first question, sure: cost of improvements plus CPI. To the rest, orienting the policy around the vanishingly rare corner cases when property values go

To the first question, sure: cost of improvements plus CPI. To the rest, orienting the policy around the vanishingly rare corner cases when property values go down is kind of silly. Our entire political system is a machine optimized towards preventing home values from ever falling. (Which does make me wonder why people feign surprise at the intended result that housing is nearly impossible to afford.)