Come to think of it, that would be the only way to conquer Dorne by blocking their access to food. The Dominion will not trade with them, their fertile lands burned and their ports blocked without being able to receive food from the east, not like in the past that is, Dorne will have to surrender or starve. Viserys could get to negotiate with the Dayne (since they are the only ones with fertile land) to be the new lords of the Domain in exchange they will open trade with the Domain and the Martell eliminated or downgraded to a lesser house.