Honestly? I think Black would've been much more tolerable for me had that been the case.
The reason Black almost killed the Pokemon series for me was the fact that I had no way to catch some of my favorite Pokemon and raise them, as there's no backwards compatibility 'til the non-existent postgame and I didn't have Wi-fi. So I was stuck going through Unova with a starter I only barely tolerated and picked because its final form didn't look and feel as stupid as the others (Serperior, breaking my tradition since '98 to choose the water starter on my first playthrough of a new generation), catching a bunch of Pokemon that I didn't really like (there are a scant handful that I actually enjoy this generation), and raising them to fight a bunch of other Pokemon that I didn't like either.
And all this would've been fine if Game Freak didn't decide to slack on designing these newbies AND cut us off so we were stuck with them.
I thought the storyline could carry its own weight, save the disconnect with Team Plasma and the face-heel turn of Ghetsis in the end, and would've been much more happy had all the Pokemon available had been replaced with their older counterparts.
In fact, Black 2 is the only reason I'm still with Pokemon. I bought it on a limb and was pleasantly surprised that they fixed the numerous gripes I had with how they did Unova. I can happily say that the only Unova Pokemon in my party during my Black 2 playthrough was Serperior. And that was mostly because I don't like ditching starters.
Would GF have been able to pull it off? I think so. They could've done something where the new Pokemon are programmed in already but unavailable, then release them through the Dream World/Colosseum-esque sidegame/Dream Radar/whatever. That would maybe hype up the new Pokemon a bit and give B/W a reason to be 5th gen. Then just keep Black and White 2 the same.
I think doing this would decrease the negative opinions that are going out now, but I think it'd introduce a whole bunch of new negative feedback. Game Freak would listen to that and the next Gen of this hypothetical universe would end up being just as bad as Black/White was. Black and White 2 is what it is because Game Freak heard the cries of its fanbase and fixed what was wrong.