Berkshire Hathaway as an alternative to an ETF?

Yep.

When it comes to their money, people have a fear of dying too young. Retirees much prefer the ARF to the annuity because they think they will die young. This applies to those in defined benefit pensions, not just those subject to buying in the market. Same when it comes to the US inheritance tax on non nationals. They think they will die and owe money to the IRS.

Firstly, unless in bad health, if you are young, it is likely you will live for decades to comes. As you get older, those odds decrease slowly.

Second, non compliance of this tax is rampant. If you hold shares through a EU based broker, I wouldn't even be thinking of this tax. If you think the IRS will be aware of the disposal of shares held in a custodian account for a deceased Irish person, you think the IRS is a lot more efficient than it is. Look up a few articles on the state of the IRS and the recent funding that has been granted to them. They have bigger fish to fry.
 
For the trusts you've listed (which are global) sterling is not a risk. Sterling would only be a currency risk for trusts investing in the UK only (like FGT).
The main risks I think about for Trusts are
1. Possibility in the future that the Irish Tax regime is adjusted to punitively tax them
2. Trusts often use leverage (1-10%) which can juice your returns on the way up but magnify losses on the way down
3. They are actively managed so manager risk
4. Some of them are not particularly well diversified. (SMT only holds 48 stocks, FGT only holds 24).

I personally use BRK and other single stocks for my US exposure and Investment Trusts for my global exposure.
And I avoid ETF's because of the nasty tax situation.
 
What other Conglomerate stocks did you look at?
 
Doesn't the Ireland - US double taxation treaty (mostly) eliminate the estate tax issue in any case?