Another idea (which I'm sure is not going to be popular but is probably a pretty good one): choose countries where the head of the state is stable: eg. Open Kin

Another idea (which I'm sure is not going to be popular but is probably a pretty good one): choose countries where the head of the state is stable: eg. Open Kingdoms, like Morocco, where the royal family is there for more than centuries and has a history showing a welcoming attitude towards international gatherings / foreigners, or where most people can get in without needing a visa.