This is absolutely true, I was thinking you could certainly structure it differently than the annual tax system we have now, and certainly in similar property taxes there's an assessment problem.

I don't have any answers for those things, but it's an interesting thought experiment - what would such a thing look like for relatively easily valued assets vs very difficult to value assets, etc

Perhaps you could simply structure it as a transactional cost, but of course, that causes overhead on every transaction. Backdating would be ruinous and cause people a strong incentive to transact often which is probably perverse.