My understanding from one of the previous updates is that you will at a minimum lose some dialogue or have dialogue that makes no sense (barbarian gale being treated as a wizard), but quite possible for some characters they will cut significant things. IMO you are much better off leaving them to start as the canon class and multiclassing so that everything works / makes sense.
I was actually thinking that as well. I won't probably respec any of the origin characters but if I do something then it will be multiclassing most likely.
It's just interesting to know how much of a story we will loose and how much will still play out but might get messed up.
