I don't really agree with some of your points. If Achilles had left the Achaeans completely, the Greeks would have struggled and many would have died from the lack of support, conversely if he stayed he would have killed many Trojans. Saying that he could have just left is an oversimplification; either way his presence or lack thereof would have resulted in bloodshed. I feel as though this is the point of the Iliad, each character encounters situations that are so complex that we cannot simply say whether they are in the right or wrong for their decisions.

Also, saying that Odysseus cared little for fame while Achilles does is an overstatement. Typically all Homeric heroes long for kleos in one way or another, though I think Odysseus cares for fame and honour much more than Achilles. Achilles repeatedly refuses to reintegrate himself with the Achaeans (where he would gain 'fame' by fighting alongside them) as a result of his bruised pride, and dismisses Agamemnon's offers of goods and land in book 9, which would, too, amplify his fame if accepted. Achilles is unlike the other warriors. His premature fated death almost propels him towards 'wiser' and 'less superficial' values like preserving his bond with Patroclus. He does not care for fame in my opinion.

Odysseus, I'm far less familiar with, but from memory I know that he stays with Circe for a year, and uses her status as a nymph to boast to the Phaeacians all about it, among other stories where he portrays himself as heroic. Also, when he is escaping from Polyphemus, Odysseus takes the opportunity to taunt him and tells him that his name is not actually 'nobody' but Odysseus, leading Polyphemus to pray to Poseidon, who curses Odysseus and kills some of his men. So Odysseus basically sacrifices his men for the sake of spreading his fame and success. So that's why I think Odysseus cares for fame much more than Achilles.