Chris Martin tried to recruit Tim Rice-Oxley to play piano and keyboards for Coldplay while they were still in school. He declined to stay with his school band The Lotus Eaters which eventually evolved into the band Keane.
If you're not familiar with Tim Rice-Oxley, he's the Samuel L. Jackson of English posh rock piano players. He would have been a great asset to Coldplay. He currently plays with Keane.
My whole point was that Chris Martin recognized his band was weak at piano/keyboards. When Tim Rice-Oxley turned him down in order to stay with his student band (that eventually became Keane) they settled on being a four piece band with Martin to play piano as needed.
Keane aren't for everyone but they're successful. Several British publications have listed their first two albums in the top 20 best British albums of all time. Their debut LP, Hopes and Fears is on every poll for best British albums.
I disagree. Nobody could improve on what Coldplay did or do: they are ´music for people who don´t really like music´