Honestly i would go for a church/sect. I have friends and pardon me for religious people here but it is tax free. I can profit but i would also help the poor and give free services and shelter to them. I think its a sustainable income and with correct processing.
If you want a tax free business, I think you can setup a cooperative, or as you said a foundation. A business that hides in the back of charity group to escape taxes

. Tax Evasion, anyway in my country it happens.
As of the service/business, i would like to have a buy and sell of native products, i would buy the raw products in a very reasonable price, create a job for the natives to increase their way of living. Mostly it will be handicraft or some products that has something to do with the natives skills. T