Yes, GiveDirectly is the charity we had in mind. There are many ways to accumulate this capital. It could be a wealth tax from the government, donation/pledge request from the ultra wealthy where if you get some onboard more will hopefully follow suit, or it could be an investment fund in humanity.

Yes, I like this idea too. Are you suggesting that anyone could invest in this "humanity fund" where they would retain their capital (so if they ever needed their initial investment back they could sell their shares), but the annual returns would be used for humanitarian causes?