My biggest concern with Larian's game rule changes is that if they are the only choice (not an option), then all Larian's NPCs - the enemies we face - will be buffed in this way. So *choosing not to use feature X* is simply not an option, if you want to have a reasonable gameplay experienced without lots of frustration. The existing 5e systems (core, not splatbooks and the like) are reasonably balanced, and what I expected from this 5e game.
In particular, you can bet you bottom $ that we will face many multiclass enemies exploiting their spell casing boost (should that be confirmed).
Also making fundamental changes like this with no warning on consultation is really disrespectful to the part of the community that actually wanted a BG **5e** game.
I also don't think you should be able to repsec origin characters - their builds were part of Larian's vision. Do they not have conviction in that? Isn't being a wizard integral to Gales story? If that is what they mean, that makes no sense.