I felt it would be great if someone like Demandred could survive, and use the chaos in the years following Tarmon Gaidon to carve out an isolated kingdom for himself - maybe where the current Murandy lies.

A place that is insular and which can be a haven for remaining outcasts, mercenaries, evil characters etc. Kind of like the remnant Orcs after Melkor dies, or the Witch King of Angband or some such place in LoTR.

I thought it would be a great idea to have unresolved elements such as this remain to plague the world in the time when the world is unsettled, and everyone is battling over the Remnants of the Third Age.

Having every member of the Chosen wiped out, and the world going straight into a Golden Age of steamengines, universities and progress will be so boring.

I was hoping for a Dark Age, where strife continues for centuries, until the last Forsaken finally dies of old age, bitterly reflecting on his deathbed on what might have been had his Master won, and given him immortality.