Alliance 'Hub'
if you were to have a central hub for each alliance where the alliance leader could declare war on another alliance, and proclaim alliance with other alliances.
this would mean all members would be know of their enemies and allys, you could also have a list for personal players, although this would be harder to do.
but you could add a button in the 'enter' section on the map that says declare war, and then go onto, alliance, or player.
when war has been declared the whole alliance could then get a notification.
i also think the idea of a, 'head' vice, or a 'co-leader' would be a good idea, the general idea would be that they can resign mines and declare wars etc.
thoughts... ?