You can try my 16 countries, all are open to corps. My main country is Anarchist Republic of Rome. Some will be short on population, but send through the request anyway and I will buy more population as required. 0% tax and enough workers gauranteed.
The State Of Punjab, 85% employment and 0% tax. Message me in-game if needed. Also will be buying 2 million more in the next couple game months so just send me corporation request. Also feel free to bid on any state corporations or anything else, message me. Thanks, AmericanSingh
Skyria 0% tax, get around 10k high tech engineers every in game month and 2.4k high tech seniors every in game month. Also I've been trading with a certain country with about a day's worth (30k engineers) for the low/medium/high lvl workers literally every day. So you can always expect a large labor pool.