Thunderbird Is mainly remembered for being killed off.
If BooBoo Stewart Is playing Thunderbird that Immedetly opens door for him to
be sacrifial lamb Ins tory like Darwin was In First Class.You drop Banshee and
Havok but bring In Thunderbird
There Is likely a reason for that If he's Thunderbird.
Since next film will likely be In altered present If there Is a so called correcting of things at end of film There would be no reason to keep Thunderbird alive.
I am getting ahead of what some may say If Thunderbird makes the cut and bites the dust.