I think with so many vocalists in the band, it wouldn't hurt if they also split some of the vocal duties when they hit the stage. Given Nick and Rikard some of David's vocal lines just to give the band a more vocally diverse feel and to separate itself from the Longdon-era performances of these songs. It could help the band rebuild its identity, which was already headed towards being a multi-vocalist band in the last two albums anyway, especially ending WTTP with a song mostly sung by Carly. I think future albums might also work with that framework as well - have some songs sung by Nick, Rikard, Carly, Claire, etc., as well as Alberto.
-Marc.