An idea that is probably not that difficult to include is that continents are not always the same. I explain the principle based on the classic Risk Map, but it could work on any other map as well.
Idea 1: When you create a game you can toggle the option 'continental drift'. The continents are then not 100% the same as normally. For example South America now includes Central America or Australia also includes Siam and India. The amount of extra armies that you get can either remain the same or be adapted based on the continent size.
Idea 2: Maybe a bit more 'outside the box'. It is possible to have the 'continental drift' during the game by a unique selection of cards. For example when one player plays 4 cards with the same 'icon = artillery, cavalry, ...' the continents drift automatically. The nice thing about this is that some players will own 'by accident' a continent or will not own a continent anymore.
Main reason why i would include one of the above is that it might change the standard gameplay and strategies used in several maps.