There is only one condition that I'm okay with Wally's hair out, and that is if his identity becomes public again and he just doesn't wear a mask at all. Otherwise, full cowl.

His hair coming out of a mask is reductive towards him. While not with many, many other comic characters, it is with him because going from his KF outfit to the Flash outfit was symbolic, not just because of the colors, but the silhouette. He may not look like a sidekick, but he still looks Flash-lite.