Reaper wrote:
No it wouldn't because sea stone is unbreakable right so no matter what Ace couldn't leave but that key there would allow him to escape. Yes killing luffy would prevent him from unlocking ace then but later on theres the possibility they'll do it again and Mr. 3 was there so killing luffy would only prevent a small delay for ace to escape and if he did then he could easly escape from being crushed with his fire powers.
then what did changed now, I ask? kizaru went and broke the key, one second after that ace is free again along with Luffy. it would definitely be way way better for marines if he had shot Luffy.
and for 1st, Luffy was lying on ground there, aokiji has just gone and impaled him pointlessly. while he could freeze him.
and those guys must be quite master at haki, they would definitely stop Luffy reaching platform if they bother. including sengoku.