We've seen characters that people don't even like get weaved into the Marvel Universe.
I do believe that new characters can sell, but same people who are upset about what Marvel is doing now would still have a problem with new minority characters. The same tried language about things being "forced", "PC", "shoved down their throats" would be trotted out.
That's why myself and others have been saying for years that Marvel's best bet is to actively go after new fans rather than trying to appeal to those who are against diversity no matter how it's done.