I also don't really think allowing Origins to switch classes is a great idea. For many it won't make sense. Some ideas from fans are ones which should be ignored. Sometimes Larian's desire to give as much freedom to players as possible can result in a weaker story.
If they're really intent on allowing class changes, I don't remember who posted this, but the best idea I heard for this was that Origins always start out at level 1 in that class, that class can't be changed, and only starting at level 2 do you get to multiclass into a class of your choosing. You would be able to change your abilities and most other things, but the level 1 class would be fixed and unchangeable.
