the allies in 1814 and 1815 had to figure one of these out. At first they put Napoleon on an island easy to depart with 1000 of his hand picked men (not sure the exact number). He departed and came back to France and scared everyone again. Welp...don't make that mistake again. The solution is to find an island very geographically remote -- St Helena in the South Atlantic. So, possibly we could put him in Antarctica or Wake or Midway Islands. Maybe Bikini Atoll?