kunark at the very least would be pretty epic imo. three different roaming world dragons (Severilous, Talendor, Gorenaire), two dungeons with raid mobs at the end (Sebilis had Trakanon and Karnor's Castle had Venril Sathir), and then an entire zone dedicated to raid dragons (Veeshan's Peak).
and kunark introduced the Epic Weapon quests, which spanned multiple zones over every continent
would be a whole lot of art assets to build though, which i imagine at this point is the main roadblock to adding new content.
i don't know how to code, but i'm decent with image manipulation and i'm sure a few of the rest of us are too... if you needed help in that area i bet you could find it.