(Can I just say I'm over the moon about Richard Armitage and Mark Strong? Most of the roles I was pretty flexible about, but not those two!)
Most of the female roles are going to be small roles, with the exception of Galadriel, Lúthien, and anyone whose role we expand (Haleth, for instance). There are a grand total of 2 girls among Finwë's grandchildren (Aredhel and Galadriel), and likewise 2 among his great-grandchildren (Idril and Finduilas [depending on her generation, again.]) For the most part, the wives have non-existent roles. It's better with humans - Andreth, Morwen, Haleth, and Elwing (okay, so she's part-human) are all going to have interesting and uniquely tragic stories.
I agree we're stuck with a relatively few number of female roles, but I don't think we can help but expand many of their stories. Not just to be "PC" or current or whatever; but because they're
interesting, and, frankly, require elaboration once we leave the epitomizing style. Aredhel, for example, as the Noldo princess trapped in Gondolin? That sort of comes out of nowhere in the published Silm -- which works there, but we'll need to flesh that out. Maybe give her a story line or two in Gondolin in the seasons leading up to her capture by Eol. Andreth, too -- it would be awkward to have her as a young woman in love and then completely disappear until she's an old lady lookin' for a fight. I also think Finduilas needs fleshing out: it's heavily hinted in Tolkien's writings that she was the possible "breach in the wall of fate", and that will work/be conveyed best, I suspect, in this narrative style if she's given her own storyline.
And, of course, we're completely forgetting the women of Numenor: if we don't turn Erendis, Ancalime, and Miriel (at least!) into complex, sympathetic, and flawed characters, what are we even doing?
Maeglin is a weird messed up emo kid. So, yes, he's a villain (eventually), but he's a very particular kind of villain.
I love Tennant, but I agree he's too old for Maeglin. My head-image is rather close to Ben Barnes, actually... But Dorian Grey Barnes, not Narnia.
EDITED: Some of my text got eaten, somehow.