My first instinct pegs Aral as Gryffindor (although I buy the argument about him being a Puff, his early self strikes me as a bit too violent and idealistic (and violently idealistic...)), Miles as rule-breaker type Gryffindor (Miles is probably a bit -- a lot -- like Harry; the Hat probably stalled between Gryffindor and Slyth, and Miles would sweet talk it into sorting him into Gryffindor, because, you know, Vorthalia the Bold. Plus, his lack of ambition for Gregor's camp stool). Illyan as a Ravenclaw (inclining towards a Slytherclaw, really)- he can be sneaky, he can be hardworking, but he sure loves his data. (I can actually see him volunteering for the chip, because of the sheer shiny attraction of something that could possibly make him smarter.)

Cordelia I'd place as a Hat-stall. She reminds me of McGonagall, and ultimately I'd slide her into Gryffindor (with her views on the Vor, she's probably not enough of a pureblood fanatic to be Slytherin although she certainly has many characteristics of one), though it's a very close shave with Ravenclaw.

Mark I'd peg as a Slytherin. He's certainly sharp enough, he doesn't share that brand of heroism that Miles does (though he has his own). Strangely enough, I can also see him as a Hufflepuff.

Ivan - is really hard for me. He screams Hufflepuff to me, except for the laziness...

Having said that, I think what this very fascinating discussion shows is that - people really can be placed in all kinds of different Houses, depending on what you define as their defining characteristic and the the House's defining characteristic :) It must be a pain, being the Sorting Hat...