Actually, you can operate GUM-HKG or SPN-HKG as non-ETOPS if you stay within 60 minutes of GUM, YAP, ROR, CEB and MNL. However, it does add about 40 minutes to the trip. The extra fuel burn and time required to do it made Fly Guam not able to compete with United Airlines and Philippine Airlines.
I hope Saipan Air does well. Saipan has not had much jet service since 9-11. Also the island economy has gone south as the US has removed some of the preferential treatment from the garment manufacturing industry that used to be in there.