GP probably spent 5 minutes writing that comment. I'm sure a proper policy naker will put more thought into it and consult lawyers/economists when making a fleshed out plan.

There's always loopholes. An internet forum isn't the best place to try and close every hole.

it is already more or less the case, but I argue that it's for the benefit of the living holder, not the heirs. A lot of the incentives to have huge, untouched inheritances revolve around dynasty effects, exactly the kind of behaviour we want to curb.

I'd go further and say that "unearned wealth corrupts" is a well known effect, and (apart from the small subset of rich people who do not care about their kids corruption and intrinsic worth apart from them being the vehicle of their dinasty) we see that divestment into charity / foundations are the modern preferred way for inheritance management, both sparing the kids somewhat (being downgraded to a multimillionaire is not a hellish situation) and gifting them cultural influence. A sovereign fund could scratch that itch somewhat.