Leaving aside all that ethical stuff....

What do you do when the 'winner' of the lottery runs away? The people who sign up will be weighted towards those who believe that they can escape, and once you have won the contest, the calculation becomes a risk of 100%, not 1%, so the motivation to escape is high.

Politically, asking people from a very poor country to accept that people from rich countries (or perhaps even worse, a rich upper class) are taking their countrymen apart for spare pieces is almost certainly going to increase the risk of public unrest.

And finally, while this is a solution, it is probably not the best or most workable. I suspect that you could get nearly equivalent outcomes in ROI and end up helping more people in both countries if you either paid people for becoming organ donors registered at the local hospital and with a contract specifying that you get the organs, or alternatively, paid families post-death for rights to organs. This might result in a delay in getting your first batch, and would mean more paperwork and more in depth ties with the local medical systems, but would cause much less social/political brouhaha.

However, I do support you setting up your foundation simply so that when someone proposes the solution in the above paragraph, people consider it to be the sane option :-)