Yeah, there’d need to be a bit more flexibility about payment schedules, I think. If your stuff appreciates you’re definitely richer, it’s not just theoretical before selling in today’s complex financialised market. It would have to be legal to owe more than you pay for a long period if there’s a good reason like “my house isn’t subdividable and I am house poor”. Taxing something hard to value would be a stickier wicket, but you could just leave the amount owed for your now legendary sports card undefined until it is defined (realised, basically, but without needing to pin it down in the legislation).
And capital gains tax should have to be settled up before your estate closes.
Analagous, if your house went up by $150k, then they said “oh, you ‘earned’ $150k, you owe $80k”, your only way to cover that would be to sell the house, which isn’t fair because you were living in it, not using it as a financial instrument.
Primary residences are often exempted from financial requirements for that reason.