Well, you posted a link to the traditional classic norse mythlogy, not the Marvel one, so I wasn't sure if that part of her story remained truth. I did some research, though, and found out that Marvel's Brunnhilde also has a history of having her spirit/soul/essence inside of other people's body. So while they could do that and claim it's mythologically accurate, the whole blackface thing could still be a problem, depending on how they handle it. If they make it as just another story of Brunnhilde inside of another person's body so she can eventually return to her own, fine, but if they do that for the sole purpose of matching her to her MCU counterpart because ''they don't have enough iconic black female figures'' and that is going to be her definite body from now on, yeah, I'll still argue that this particular kind of representation would be problematic, because it would essentially be a white woman posing as a black woman for representation. I mean, a black woman with a ''white soul'' in a society where african-descending communities still deal with the fallout of historical oppression because they weren't white... yeah, this wouldn't sit well with many people and I can understand why.