I don't think it'd be Cobie Smulders, as she's tied to How I Met Your Mother for the next 50 years.
Yeah, I know she's on HIMYM, but I thought she would have summers off [i.e. how she did The Avengers]. Whedon usually works a year in advance: he could film her parts of a story during 'off-season time', then insert it when the season is in production. Plus it is always possible for actors to get breaks from series (depending on those running them) for a few weeks, where she could have guest shots.
I just think a SHIELD show without Fury, Coulson, or Agent Hill would seem a bit too 'off'. Those having seen The Avengers film know what's up with Coulson [if anyone mentions it: spoiler it, because there
are people who haven't seen it yet]. And Sam Jackson is highly unlikely to be remotely regular on a TV series (if he shows up at all except in possible flashback to 'just starting' [i.e. played by another actor]).
More Coulson=loyal viewers.
Yeah... and Whedon does LOTS of flashback stuff in his series, so not out of the question.

Hopefully it doesn't turn into CSI: Marvel. They are probably not going to use any super heros because they will want to save them for big name stars. I can see this turning boring pretty fast.
[To the highlighted part:] Have you never seen a Joss Whedon TV show?

'Boring' is not in his repertoire.
I could see them using B and C list superheroes and villains. Ones that wouldn't show up in the movies.
Just please, cast Bruce Campbell as a retired superhero or something!
Oooh! Bruce Campbell as an aging original Human Torch (the synthetic one in the tube at the NY World's Fair seen briefly in Cap Am)!

That'd be great.