So, this was a big deal for me. I was concerned. Some of my favorite sites I visited absolutely trashed this concept. However, I really believe it fits into the game particularly for specific races.
A couple of examples:
Argonians were slaves of the Dunmer. Excellent reason to leave? Umm, yes.
Dunmer are elves. Why not jump ship from the Ebonheart Pact to join the Dominion?
There are numerous possibilities to justify having other races in each Alliance. The major defense I hear popping up over this is "faction loyalty". That is a decent argument, but really one is not signing up because it is a race war I would hope. This is a big world and each race moves around. I hope nobody imagines they would never see a Khajit in Daggerfall or an Orc would never show up in the Dominion. From a common sense perspective this should not be irregular if anyone has played any TES game.
I do not wish to come off as 100 percent behind everything in the game, but this is one point that is generally brought up on some of the sites I frequent regarding the game that just....well, I have a strong opinion on because I believe it is baseless.
Now, as to including it only for pre-orders I think that is fine, but there is a strong argument against this, which I am not going to touch....