Gai gates...

[THM Nindo]

Gai or Lee will definitely be able to open all 8 gates without dying. Just look at how Chouji survived the butterfly transformation after it was said that he'd die if he used it. Gai use of the gates is impressive since he seems to activate them as if it's nothing.

It's not using the butterfly transformation that kills you, it's achieving it by taking the red pill.
And he was basically dead, he was only save thanks to Tsunade. (I still think the story would have been better if Choji stayed dead... more drama!)

As for Gai gates, I can hardly see how he could deflect 5 bijuu dama, but we never know.
He might have been too confident about his skills...

I can see the "deflecting two bijuu dama into 2 other biju dama" suggestion work somehow.

[LnDRash]

8. The Gate of Death (死門, Shimon), located at the heart. Releasing this gate uses up all of the body's energy. It makes the heart pump at maximum power and exceeds the power of every other gate. Opening this gate gives the user power that is even beyond the five Kage, but comes at the expense of the user's death shortly after.

I don't see how one could possibly survive this... since it depletes all of the bodies energies, which means every single organ and cell will shut down and stop working.