I think a cold war vairant would work on the global scale.
We have Nato, Warsaw, USSR, USA, China.
Then Communist Nations and Capitalist Nations
We start in 1961 during the Bay of Pigs.
Nato, USSR and America both have a 3rd unit option. This is called a nuke. USSR gets 3 per year, USA gets 2 per year and Nato gets 1 per year,
If they fire it at a territory any army in that territory will be destroyed, however there is another catch, any sc in that territory is also destroyed.(it becomes a non-sc territory)
Units: Given that modern warfare is very complex, I think there should be a multiple range of units:
Land:
Army: Standard rules apply
Spy: Classic CIA vs KGB, Nato, America and Russia all start off with 1 unit known as a spy. This unit is invisible to all non-spy units, however the main point of the spy is it informs you of the nuclear stock-pile of the enemy nation it is currently in. Each country can have a max of 1 spy at a time.
Naval:
Fleet: Standard rules apply, this unit can also carry aircrafts, bringing them closer to their intended targets.
Submarine: Invisible to all units except for other Subs, this unit can carry nuclear weapons (when building a sub, you have two options, a regular sub and a nuclear sub. The nuclear sub requires both a sc and a nuke. They look the same so the enemy can never tell which is which). If a nuclear sub is destroyed, the player looses 1 nuke from his nuclear stockpile.
Air:
Air unit cannot attack enemy territories, they can only support attacks (they can only support a defense if there is an enemy air supporting the attack). However they count as 2 supports so are very useful in combat. The maximum range of the unit is 4 territores (it can support any unit that is within 4 territories of the territory it is in).
Nukes:
Nukes are a powerful unit that certain countries get each year. To represent the situation at the Bay of Pigs here is the current nuclear stockpiles of countries at the start of the game:
America: 15
USSR: 8
NATO: 4
Communist Countries: 2
Every year USSR produces 3, America Produces 2 and NATO produces 1.
There is an Armageddon counter on the nukes, once 40 have been fired, all nations becomes 'defeated' and any points invested into the game are lost, by all players.
People should be very cautious when using nukes, knowing full well that it could end the game. Players can use this to form 'stalemate lines' saying if you continue to attack me, I will fire my entire stockpile ending the world. Include me in the draw OR ELSE!
Nukes have a maximum range of 3 tiles, making nuclear subs sometimes the only way to nuke enemies.
Lastly alliance:
Alliances are very complex, and to encourage usual diplomacy here are some add rules:
USSR soldiers can enter Warsaw lands without taking them. However if Warsaw ever attacks the USSR, then they can start attacking back.
However if Warsaw ever attacks the USSR then they will loose their SC in East Germany and Bulgaria, encouraging them to remain a vassal of the USSR.
All other standard diplomacy rules apply. The map would probably some variant of the world war 4 map.