ARTPOP
1) Aura
2) Do What U Want
3) Mary Jane Holland
Mess.

Aura could have scraped the same position as Applause without the longevity, DWUW would have done the same and MJH would not have even made one iota of impact on anyone.
Self Titled
1) Blow
2) ***Flawless
3) Jealous
4) Mine
5) No Angel
This would have been hella successful until No Angel, but it would've targeted all markets. Blow at Pop, ***Flawless at Urban, Jealous at Adult Contemporary, Mine at Urban/Urban Adult Contemporary and No Angel at Urban Adult Contemporary again. Poor Drunk/XO though.
Rebel Heart
1) Unapologetic Bitch
2) Illuminati
3) Living For Love
Cute era I guess. UB actually probably would have slayed with the right radio edit, video and performances. Illuminati would have been cute for a bit of buzz with a few cameos. LFL would be weird to end an era with but oh well.
FOUR
1) No Control
2) Clouds
No Control as lead would have given them a number 1 in the US and UK simultaneously. Clouds would have done well in the UK too. Anything is better than what we got tbh.