I don't know about the whole "Kono being separated from the team at the beginning of each season" thing. I've heard in the past that Grace Park has wanted out of the show, so each time they pull this, I assume they are writing Kono off.
I think the opening sequence was at least some variation of bullet time. I guess you can use CGI characters if they are faceless/masked.
I'm certainly hoping they're not going down the brothers route. But if they don't, I have no other ideas to explain Wo Fat's connection with Doris.