Pixie, I do not think you can assimilate leaving a Will of YOUR possessions to whomsoever you decide with something like FGM. It is comparing apples with pears. In this country testamentary freedom is a law that has been jealously protected by the Courts for centuries - despite the fact that the Wills Act was made in 1837, it has been updated and our legislature has moved with the times. It is not mere "tradition".
Frankly, I'd be a bit narked if, by her will, my mother wanted me to have a particular piece of jewellery to remember her by and HMRC said "nope, we are melting it down for scrap cos it's ours now".
Taxation is one thing; the state taking complete control over testamentary freedom is quite another. I do not mind if the rate of IHT is increased; there are sufficient exemptions available to ensure that most family businesses and homes remain within the family.
However, if we are working on the basis of 100% of what you own goes to the government, I think it's a terrible idea. It will not affect the really rich, since most of their stuff is already tied up in complex family trusts. It will make the divide wider. The working man who has saved hard to buy his own home to pay for his care fees and then pass the remainder to his children will still lose out and more so. The hugely wealthy will just use offshore trusts. This would harm the lower and middle classes rather than actually tax those who can afford it.