Like the person above, I'd like a BAMF! Ianto - specifically, I'd like to see him (and the team) dealing with a second Cyberman invasion, with all the memories that would bring up for him (the friends lost at TW 1, as well as of course Lisa). After he realizes what's going on (and probably breaks down a couple times), he leads the Team in the assault on their base, avenging her and all those he's lost.

That would be awesome.