Since he only made his Silver Age debut in the Fantastic Four, apparently some argue that he's not included in the Fox deal at all. (In fact, they were working on setting up his own movie at Universal, apparently.) If they're looking for a way to launch Namor with this movie, then I can understand... although I hardly think that the WWII ties are necessary for that character.

Namor and the Torch are such big concepts, however... how easily are they just dropped into a film? Looking back at my example above with the X-men, once you've explained the "mutant" idea, you can simply drop in as many bizarre powers as you like with no further context needed. I guess that the best I can imagine here would be having an early version of SHIELD (or just the OSS?) introduce Rogers to the idea that they have been gathering a team of unique individuals since before he became a super-soldier, just like Fury is apparently doing in "Iron Man" in preparation for the Avengers movie. I'd still think that you maybe couldn't actually get into the fact that Namor was king of Atlantis or whatever.

Since the interview mentions 6 Invaders, I'd say:
Cap
Bucky
Namor
Torch (some version, if they can)
Union Jack (or some other British operative)
A soviet operative (an earlier Black Widow?) to keep go with and "allies" theme and tie into the present.

I'm sure Nick Fury must show up in WWII at some point as well, with his Howling Commandos.