Sure it could be done, but why? There's always going to be a "best" setup for raiding. It can be done without the best weapons, but who wants to "three, maybe four phase" the boss at GoS when you can do it in two? The challenge? That doesn't seem to be the "point" you're trying to make. Now, if you were talking about putting a team together with all blue weapons and armor to go into Crucible, that'd be different.