I think that a single player RPG could be good, if it was done well. Jobs and sidequests could feature together, like you can get different quests depending on what job you have. Also, jobs could deliver a salary, every few minutes or something. Obviously military could come somewhere in it, maybe even a twist like an invasion, though don't make it a cleché. You could even use time for something like development in military units. Use the whole island, and a good idea could be to use relationships or maybe a family, but make sure you have a point to it, somewhere to end. Make it a complete experience.
I'd love to play it if it's done well, and ensure you have a good replay factor, so people will play it again and again.
I'd definately beta test it.