I wouldn't mind having Michael back but I wouldn't be too excited about Walt since they'd probably have to use another actor to play him (which I would not like). The show's still technically in real time and I think it's only been about 4 months or something? They crashed on September 22, 2004, and as of Wednesday's episode it is only December 10 2004. (Thanks to
www.lostpedia.com hehehe!) Walt is only 10, but from the first episode we saw him to the episode where Walt and Michael were sent away, it was already obvious that Walt the actor had aged significantly. This would pose problems if they decided to bring Walt back, as he'd look 3 years older.
And in regards to who the Others want, if they wanted people who weren't troubled or angry they definitely would NOT have taken Jack. He's one of the most troubled characters of them all! (Ex. his wife leaving him, his father dying, struggling to accept his establishment as leader among the Losties, the Kate/Sawyer triangle).
You have to realize that virtually every character has had a dark and sad past. That's what all the flashbacks are for!
Anyway, I'm excited for next week. We finally learn how Locke became a paraplegic! (this was in the episode preview for next week)