Fett wasn't a fan favorite when they killed him like that. His following came later. Given a second chance ... Fett would live, or at least have a better death (he was a villain, so they'd still probably kill him ... just better).
I don't think Daryl's much like Palmer. They killed Palmer because his story had played-out. He wasn't President anymore. He'd already been a 'consultant' to the new President. There was nowhere to go. I can't see Daryl's story doing that. Curtis wasn't as big a player as Daryl ... though Curtis's death was one of the few I really didn't like on 24.
I can see the Tony Almeida comparison ... Jack's sidekick, confidant, substitute leader, etc. But ... they didn't kill Tony, even when they seemed to. Having Daryl pull a Tony and become so scarred by some sacrifice that be becomes a revenge villain, and mirror of Rick, would be an interesting twist. Pit Rick and Daryl against each other. Especially since Jack Bauer followed Tony down the same revenge-killer path by the end of the series. Rick could do the same ... for a rather dark ending to a dark series.
SnakeDoc