I could've imagined Ariana feat. Nicki but it's Jessie J feat them.
This song is gonna be a mess or a hit and Nicki is so doing the bridge, something like Iggy on Problem.
I just hope Ariana + Nicki have the right parts in the song. I don't want them to overshadow Jessie, otherwise people won't even recognize the song as a Jessie song, and she needs people to remember that it's her feat. the other two.
I feel this might end up as Problem's little trainwreck sister, I love Ariana, but I feel she and Jessie will do some oversinging, with Jessie doing her vocal acrobatics and Ariana doing various random whistles, with Nicki actually ending up as the highlight
I hope it's Jessie on verses, Ari on chorus, and Nicki with a rap verse in the bridge. 
hopefully this is different.