I am a conscious because I am conscious. Similar to how I am an autistic because I am autistic.
I would argue, though, that doesn't make conscious a noun, but simply uses an adjective as a noun.
I’ve never heard that usage, it doesn’t sound right to me. (Relatedly, “an autistic” is generally considered dated / mildly offensive / just incorrect. Better is “an autistic person”, which makes it an adjective again. There does exist the noun “autist” which I do hear occasionally, but not from autistic people as far as I’m aware, so would probably avoid as well.)
Isn’t it an adjective on both? Being conscious because you have consciousness. Otherwise you’re repeating the same thing. I’m happy because I’m happy. I’m pink because I’m pink? Disclaimer: ESL