What would be cool is if act bosses were bindable.
With lowered stats of course.
Blizzards fun police motto would never allow it though.
Edit:
As if we go by lore, blizzard refuses to stick to it and remove options instead of give players more choices to play their games. Leaving binding demon to only the usual demons. This had potential to be a really fun and unique skill seeing act bosses run around in town xD
Blizzard polices practically nothing. Usually (much like lock balance), things run rampantly unchecked for entire seasons before even addresses. In truly surprised they even bothered to fix hork unreliable they fix stuff, so saying theres a fun police is a stretch...but they cant do it because those mobs are tied to quests. It would bug quests if diablo for instance didnt die but just got poke balled.