The reason why I ask is, because the Government would need to make this revenue neutral. It would not get any money from getting rid of the "planning" industry. Indeed, it would lose income as the businesses fell, people would lose jobs and pay less in income tax.
However, what would happen, is the need for more civil servants within a Government department. This would cost money to set up and run. And yes these are jobs but these jobs need tax payers Monet to pay for them. As context DCMS has just over 1,000 staff and cost £159m to run. Of course it wouldn't take a whole department but this gives context of just how money would be needed to support this.
So coming to the straight maths of this proposal. An estate is currently charged at 40%. So lets take an estate of £1.5m. Lets assume that its a man who's wife has died and they have used the £1m allowance. That still leaves a treasury income of £400,000. Using this new system, if that man had 4 children they would each be liable on £250,000. To get the same amount back as the £400,000 from the system we have now, each of those people would have to be taxed at least 30%. (They would each be getting £375k, be liable on £250k and the tax shortfall would have to come out of that). So, how much more would it take for it to actually work and then generate money to "give to the poor". It would end up being a system that would hardly pay for itself very quickly and need more and more cash to sustain it. Its stupid, unworkable and just plays on people's perceptions that it would be hitting the big guys.
Someone will argue that its a never ending pot of cash as people will get multiple inheritances. Except most don't. And anyone who does will probably move away so the treasury will then get nothing.