GoT maps are overrated.
They arent overrated, Dameon's work contributed to its success, you can make easily any GOT scenario you want.
Of course if you are not familiar with this universe your opinion is different than most of the people who play his maps (and I still believe his maps are the most famous RP maps, just if you check his maps' rating and how many games are launched with his maps everyday).
The modern diplomacy rules werent invented by them, they slowly appeared as Warlight allowed to play games with more players (from 6 to 24, then 40), but there is a story about the possible origin of RP rules first made by a player known as "Soviet Russia Buddy" (check Warlight's wiki).