I think these are coolI'd be interested to see a gray alternate, but all the mock-ups I've seen using gray have been off-balance and boring/bad.
Washington State has the best use of prominent gray (not counting silver) that I can think of - with their gray helmets, deeper red jerseys, and gray pants. I don't think much of the logo, and the uniforms are simple, but the balance of gray is right and novel.
https://boards.sportslogos.net/topic/90934-miami-dolphins-uniform-concept/