It's not just the practicality of have the chamber as the main event, it's the fact that the main event is supposed to be the big match everyone is waiting to see... it makes raw look BAD if six of their main-event guys (ok, bar orton) in a big gimmick match are put lower on the card than just TWO smackdown guys, regardless of who they are. I'll eat everybody's hats if the chamber isn't the main event.
Choken One, who do you think is going to have the strap after SS, then? I know Vince doesn't appear to like Goldberg on a personal level, but he hasn't exactly got much of a hard-on for Y2J does he? From a business point of view, I think he may just put the strap on GB just because he's forked out all this cash for the big lump and he might, just MIGHT bring in some ratings as champ. If he bombs, Vince can just drop him. Why not take the gamble?
On a side note, I personally hope Y2J squashes everyone else in the EC, turns face and has a glorious reign as champ. But then when was the last time the WWE did something that good? (Oh yeah, Vengeance - oops.)