Don't know about you guys, but I really like the CoT instances. I think it's cool to step into iconic events in lore and see them from a new perspective. And I have a good suggestion for Battle For Azeroth.
The retaking of the Lordaeron capital, and founding of the Forsaken.
It's fitting with Sylvanas being the new Warchief, first time players will transform into Horde characters (all undead I guess), and will let players experience how the Forsaken took Lordaeron back in the day, which plays nice with the current day sacking of the Undercity.
I imagine you play as free undead soldiers under the command of Sylvanas and Varimathras, helping her take Lordaeron from the Dreadlord Insurgents. You sneak and fight through the demons and undead, and maybe take a note from one of the earlier FT campaign maps and beat a random mob boss, only for a banshee to posess him (Maybe a player could control that mob for event or boss fight.)
Anyway, that's the baseline for my idea, build solely on the fact I like Caverns of Time. Let me know how you like it, feel free to add it to it, and please do repost if you know someone at Blizzard :P