Draw a triangle with its corners at (31.694307N, 176.499516W), (33.909868N, 178.932671W), and (35.480483N, 173.168067W). That's the area that is more than 1167 nm (i.e. 180 minutes at 389 knots) from Shemya, Wake, and Honolulu. (What is Shemya's status, anyway?) The "great circle" from HNL to Guam or Narita doesn't pass through there, but HNL-Sapporo would just clip the corner. So with 180-min ETOPS you can manage without Midway-- but still nice to have.