Exactly !! I didn't think it was too complex .

Keaton didn't know who Soze was until Keaton had been shot and was smoking the cigarette on the ship while the gas was flowing. You can tell by Keaton's reaction to seeing who was standing there. Keaton was the last of the group for Soze to kill.

It probably would have been pretty easy to piece it together when he's no linger crippled and about to kill you.

My sentiment's exactly.

MAYBE that was a reason he chose them for the mission, but his main goal was to get the rat and he needed them to achieve that. They simply had to die afterwards because they knew too much.

I thougt he killed Keaton (and the others) because they had stolen from him. That's why he sent them up on that fake cocaine mission on that boat.

The sun is shining but the ice is slippery.

Soze (if it was him on the ship) was removing all witnesses who could identify him, it's as simple as that. Keaton had figured out who the killer was by then and what he was doing - using Soze's name when he knew what was about to happen was the only small success he had left - 'I know who you are and what all this is about'.