Sorry if I didn't get what you meant about wording better.
The main issue I see is that you're preemptively thinking a character you don't seem to care would be hated because he's from a similar archetype that's been used a lot and you heard a lot of complains. Even if the sales are 95%-5% relating to Japan and the West it still makes the franchise have a good presence, which is pretty similar to how MH was selling previous to World (MH4U was about 2.5-3m copies in Japan compared to 1-1.5 in the west for example). I don't really have any marketing knowledge at all, but I think considering the few trailers we've gotten Nintendo can pull something to get people behind any character they are selling that being Geno, Erdrick, Sora, etc. I also think Erdrick if he is being in, he would have a moveset that would easily set him apart from other swordsmen.
Like I said in earlier comments, I might be a pessimistic skeptic, but I can only speak base on what I have heard and seen when it comes to Smash Brothers, and with what I've seen and heard, he would come off as negative. I wish I had more data that would see a more positive basis. Also, I have to disagree that 5% is a good presence... But maybe that's just me.
Just to summarize why I think it will go bad if he got announced.
A) It's a WHO here in the West.
B) Square has two of the most demanded characters. It's one thing for Sora and Geno fans to "lose" towards someone like Cloud because those fans know how big Cloud is. But I can't see people being as "okay this makes sense" towards Erdick due to point A. Especially if the word got out that Square used Smash in order to promote Dragon Quest.
C) I'm not arguing about his moveset potential. I'm just saying that unless I have missed an extreme good chunk, I think you and the rest are underestimating the "there is to many anime swordsmen" hate boner that goes around.
D) If people realize that Nintendo has talked to Son Goku's creator, but ended up with someone like Erdick, there will be a **** ton of "F Nintendo we want Goku not this".
Don't get me wrong.. I want to be wrong, even though I'm not a fan of the idea of getting Erdick for reasons like "obvious marketing over fan-demand". I want Erdick to go over well for his fans sake, would he so join. But I just can't see it happening due to everything I previously mentioned.
I think this also ties into why certain people get uppity about Fire Emblem in Smash as well. While it's certain grown in success and the like, a lot of people just see a bunch of swordsmen in medieval armor and think that's all there is to Fire Emblem.
I think you nail on the head with this one