The reason I play Demo is Metamorphosis. I don't know what will fill it's place if they remove it from Demos. We could become Illidan with it and now we're not special. No reason to have it anymore. We need cooler things, if there is one.
Maybe we'll have some kinda pet resource. Each demon pets will have their own cooldowns. It's like Grimoire of Service, but with every pets(including Doomguard and Infernal). You can't use them all at the same time, that would be overpowered as hell. You'll use max 3 pets for 25 secs, but you won't be able to use the same pets for 2 mins. You think this will be ability bloat? Meta abilities will be removed when they remove Meta. So, you'll have the same amount of abilities I think, but I don't know. Still, we could be CC machines.