Riot, you contradicted yourself when you disabled Gangplank. And here is exactly why.
Way back when the lore was retconned, Riot said that League of Legends could be a way for their characters to interact without actually being literally part of their world. Think about fighting games. Soul Calibur 5 for example. Ezio Auditore can fight Nightmare, but that doesn't mean it actually happens in either of their storylines.
Think of League, the game, as just having cameos of all champions.
I agreed with this idea even though many people didn't. It frees up many things to be done for lore and story while giving League of Legends a new novelty feel.
Yet, knowing this, why would you disable Gangplank just because he "died?" Because he could transform into a god damn alien and he still would be able to be played in his current form in League of Legends because of what YOU (Riot) said about your own lore. Hell, all the champs could die to a giant magical nuke, and there would still be absolutely no excuse to disable them, because YOU YOURSELF said that the game has no relation to lore. Just because you see Lissandra mid against Orianna doesn't mean it actually happened in their respective storylines.
I should mention that yes, I DO understand that you were trying to be "cool" and "unique" by thinking "Hey, what if, if GP dies in our story, he dies in game too? How cool would that be? Do you guys want to do this?" but this isn't working. It isn't working because YOU YOURSELF stated that lore has no bearing to the GAME of League of Legends because you said the GAME is separate from the STORY.
This wouldn't be a problem if lore was directly tied into the game. But you said THE EXACT OPPOSITE.