I think that what you have here is quite a harmonically unique and melodically striking piece! The main theme sounds almost like a fanfare for string orchestra which is quite unusual! I personally hear the two parts you have presented here as separate movements, incomplete in themselves but if finished, it seems like each one could stand alone. They use the same musical themes but that too is not unusual for separate movements - maybe you could make this into a divertimento with multiple movements? That's just my perception and suggestion however. Nice job!