From the spec, its sensor is bigger than Micro43, yes, its video feature is crippled, but the fact that it's not interchangable lens system and offer such a great sensor, yet the Olympus EM5 is still popular. Am I missing something?
As for the G1X battery life, I don't see it would be a problem that it wouldn't last for 1 dive, so replacing battery after every dive is not that big of an issue compare to the complexity and cost of interchangeable lens system (dome, port etc).
May be the next version of G1X has more potential?