The Singles Collection stopped at 3, so they'd be able to add:
Hold It Against Me
Till The World Ends
Till The World Ends w/ Nicki & Kesha
I Wanna Go
Criminal
Ooh La La
Scream & Shout w/ will.u.not
Work Bitch
Perfume
Pretty Girls
Make Me... w/ G-Eazy
Slumber Party w/ Tinashe
Hold Me Closer w/ Elton
It'd be enough to give the album a decent little streaming boost, even just from Scream & Shout + the Femme Fatale singles (specifically Criminal dd). But yeah... I'd be much more interested in an outtake collection. Except if they ever actually do it, I want it to be done properly. I don't really know what type of care, if any, would go into it at this point. That's why I think updating The Singles Collection feels like an easy win that'd be hard for them to fuck up.