that was the plan if we were to issues shares (which we probably must, since gathering such large quantities by donations would be a problem)
no taxes would indeed attract investors
but would we welcome illegals to our land?
I can think of a lot of people which would come here just to grow weed and resell it in other countries
Silk Road comes to mind

Yes. We are issuing shares. Out of a total area of 10 million sq.m, 5 million sq.m will got to the shareholders. There will be 5,000,000 shares, each share worth 1 sq.m.
Non-citizens will be able to travel to the island and buy weed without any restrictions. But they will have no right to cultivate and sell weed. That right will be reserved to licensed citizens.
There will be no income tax. But there will be a GST over weed sales.