Yeah, I agree with you about Roy. Here is the thing: For an ensemble show with 5 action characters, there has to be sub groupings. As it stands, each character is attached to Ollie; that is how we see them, and it is how they react to the plotlines.
If they want to keep all 5 in the series, I'm great with that, but at least Diggle and Felicity (who have a great connection) need to be able split off and be a sub-team. I'm thinking like DS 9, or Alphas, or other shows that work with that many characters. Right now they are all attached with Ollie by their own thread, and don't have attachments to each other. And hey, Syn is getting worked in here too.
Ollie/Sara, Diggle/Felicity, and Roy/Syn would make great pairings, and I could see this working on an ongoing basis. It would mean a big shift into an ensemble cast with strong subplots for each. It could be done, but that hasn't been the style of the show.
I would love if Sara stayed.