Homes are taxed based on assessed value. They are already a form of taxing unrealized gains.

Most of the population either has:

1. no unrealized gains
2. gains in a retirement account that we can’t borrow against
3. gains in real estate that are taxed, but can be borrowed against
4. a combo of 2 and 3

I think it’s fair to ask that the rich play by the same rules. You can either borrow against your gains and pay taxes on them, or not pay taxes and not be able to borrow against them.

No because the mínimum for this to apply is 100 million.

Depends on the exact implementation, but sure, you could happily write a version where an initial home loan isn’t hit, and only “top up” loans against the INCREASED value of your home is targeted.