The way I see it, you can nominate anywhere for a destination alternate without actually intending to go there in a diversion. You may restrict your final decision to divert to a slightly earlier stage in order to allow you to divert somewhere else. It is not uncommon to nominate a place nearby your destination, but intending if the event arose to divert somewhere else where you have company staff to handle you, as long as your original alternate is realistic and available, possibly even in an emergency.