I think The Thunderbolts would be great for a Netflix show, especially since they're already doing The Defenders. And now that Dr. Strange has been introduced, I think it's more likely that the other three characters can find their way into the mix at some point.
Regarding the team-ups with the movie characters - I think they've pretty much shot that down, unless it's just a quick cameo or a mention like they've done in the movies/shows already. But they have said that they will tie in together...such as the Infinity Wars will have an impact on the street-level heroes. That the war with the cinema characters will certainly bleed over into the Netflix universe. So, that should be cool to see.
The only thing I don't like about Netflix and these shows is that they're limited to only two per year right now. They should ramp up production and do at least three, but four would be better. They only shoot about 10 - 12 episodes, so it's not that much to pull off, given that they're mostly a different cast of characters for each of the shows.
RE: Characters and Teams That Should Join the MNU (Marvel Netflix Universe)