Now I have to find the spoilers.:D I'd love very much to see the good doctor in the show.

How is this going to be done? He was frozen and stored in the facility and accidentallly got resurrected by one of The Ancients' machines? He has ascended and decides to come back to share his wisdom, much like Daniel Jackson before him? He became a ghost and wouldn't leave everybody alone? They cloned him secretly?

You mean he was written off so that some cast would learn a lesson! That is utterly absurd. You were right that Shepard and McKay are the constant no matter what, Teyla and Ronin are replaceable (rembember Lt. Ford?). So who else is left to be warned?

I love Torri, hate to see her role being reduced to minimal, but I feel adding a strong and hand on female character such as Semantha Carter is essentially a good move. Dr. Weir, being not a soldier who can go on offworld missions, has long been written as a 'background supervisor' person...

That episode is called The Game.