The scenario i like the most would be of a draenor getting rebuild.. With the new zones being pieces of continents or islands that were scattered but that got pulled back to the main continents with the use of either powerfull shamanistic powers and titan tecnologie.. Or with a lil help from the ethreals..
Each new zone would have been cut out from the rest of draenor and the species and habitants would have been alone against whatever threats existed there at the point when ner'zhul riped the planet apart.. Every zone would have a demon WARLORD(hence the name of the expansion) and would be the main danger in that zone.. And we would help the local habitants figth back the demon menace not only to protect draenor but azeroth aswell..
The first zone would be like zangramarsh but with a mix of dranei crystal architecture.. That zone would be were the last big population of dranei that couldnt escape dranenor was when the planet got ripped apart.. They didnt become mutated because the crystals the naru gave them protected them from the fel energies.. They would be aliance friendly only.. The horde would get into that zone trough ethereals that wanted to understand the crystals properties and also reclaim a facilitie that belonged to them.. Both factions would have lots of demons and mutaded creatures to kill..
The second zone would be a savana like zone with lots of animals kinda like nagrand a place that seems untouched by demon corruption.. The main forces in the zone would be a lost orc clan that didnt take part in any bloodshed during the first wars and surprise would be friendly to both factions.. We would help that faction stop the demonic corruption that the Warlord in that zone was starting..
The third zone would be a big PvP zone were the aliance and the horde were in eternal battle.. The demon lord traped a aliance force and a horde force when they were stranded there during the destruction of draenor.. And using agentes in both side makes the spiral of anger never stop.. There would be a main quest on both factions to try and make the leader of their faction there understand that the war made no sense and at the end both sides killed the warlord..
The forth zone would be the biggest one and it could be divided into 2 sub zones.. Being a piece of draenor that got completly corrupted.. And was a huge legion base.. Full with demon forces ready to strike at the rest of draenor and then to invate azeroth.. The aliance gets Turalyon to lead them in the quests there.. The horde gets Alleria..
The fifth zone would be the demon hunter starting zone were you would eventualy team up with ilidan and take down a demon lord alongside him..
Sorry for typos english is not my main language.. Made this post mostly for fun.. Dont take anything too serious..