I just have to say watch us all get trolled in season 2 xD. I mean, TWD is carrying the saves over to season 2, meaning certain choices matter. So what if you could still save Lee? What if, if you made the right choices, he ends up being in the game alive? Or better yet, on the hilltop with another unconfirmed character like Molly or Kenny, depending on your decisions? Or just a random person/generic if you failed the requirements. What if making the wrong decisions end up with him becoming undead and killing your PC?
Let me explain
You can cut off his arm early on in ch 5. Then you can choose not to handcuff him, and not to shoot him. He no longer has the bite, can now move if he gets better, and can escape with the door now unlocked. And if he needs some help we have other characters that are unknown that could come to the rescue (if blood loss was problem or magically immune

) I think it would be interesting and would mess with a lot of heads to have Lee come back alive, even if just for a few minutes speaking with the PC before being truly killed off. That'd make me feel accomplished.
I know it sounds like a long shot but you have to admit there is almost no way Clem could have rescued Lee, carrying him into that store. Maybe she got help? Or maybe someone distracted the zombies to give her enough time to get them to safety?(because I think someone falling over would attract zombies!)
I think what we did will affect Lee somehow in the future. Even if minuscule.
As a whole if Lee is absolutely dead without any trace of doubt than I'd say it wasn't a mistake. He went out like the badass we all knew he was. He saved a little girl that wasn't his but thought of as his own. He risked his life countless times for her, and to me, that was a good enough send off. Despite being a believer of the "I love you" discussion, I think killing Lee in this way was a good job. In my eyes, he has redeemed himself, and I think, if only for a little while, was truly happy with Clem.