He is a sadist, plus he controlled King Riku + Army in order to kill the Dressrosa citizens.
He had no hesitation in asking Monet to blow herself + Vergo in Punk Hazard.
He knew what experiments Ceasar was doing to the missing children.
He wanted to kill a commoner because he talked bak to him...
All Strawhat members have some kind of pride.
I cannot see that in Bellamy.
It will be good if he will try to help Luffy in order to redeem himself
but i don't think he is Nakama material.
I hope Oda will give him a moment to shine but if he joins the Strawhats i will be bummed.
Also...
Greetings,
My 2 cents for Franky being KOed:
Maybe he let himself get beaten just to give Usopp+Co
a chance to complete operation SOP.
As seen in here: http://www.mangareader.net/one-piece/740/19