I would love to play such a scenario and my suggestions are:
1.Oceania has the two Americas, Great Britain, Australia and South Africa. Eurasia has Russia, Mongolia, and Europe. The third nation (hey, belive it or not, I have forgotten its name

) has Japan and China. The book tells that from Indonesia to Dakar lies a disputed border zone, where the actual fighting takes place. This could be modelled as some low-industrialized low-armed states, all in war with the three powers.
2.Orwell suggests that the three powers have no interest in conquering the home provinces of their rivals. So, a solution would be the erecting of great fortifications at the borders, possibly 6lvl forts, with AA guns.
3.I disagree with the idea that they should have all technologies. The V1/V2 is a must, the nuclear weapons...maybe not. This is not extremely accurate, yet, with such power, the borders may become extremly unstable. This should happen only at the end of the game. The research is a must for such a mod.
4.I doubt we could implement the unending alliance changes in 1984, due to game restrictions. So, maybe the three-alliance system is the best solution.
5. This is only a game suited for MP,as it will demand strict house rules (ex. not couping the enemy)
6.With new graphics and new events, this mod could be
extremly interesting...so I am hoping for the best.