That's exactly why we didn't bother. We wanted Modric but we didn't want to deal with Levy again.
The midfielder we wanted after Modric was Thiago who United scouted for about two years with Martin Ferguson attending Barca matches in person to watch him. Fergie got the deal done going into the 2013 summer as a welcoming present for the next manager, all that was needed was for Moyes to sign off on it but he turned him down.
I remain convinced that we were bringing in Thiago, Herrera and a left-back (possibly still Shaw) that summer, then Moyes saw the brief of "midfielder and left-back" and decided to scrap the plans we had and waste all summer on Fellaini and Baines, while seemingly remaining convinced himself that we were signing Ronaldo and/or Bale.
As for what the OP asked:
Replacing Beckham with Ronaldo.
"Replacing" Keane with Carrick.
Darren Fletcher's general involvement with the first team when he first broke through.
Ditching RvN for Saha/Rooney.
van der Sar.
Evra/Vidic.