If they are about equal I don't know how you don't preserve Armstrong for another year. By default I feel all QBs should come in and take a redshirt year. The ones who don't face special circumstances. I think that is such a clear-cut, easy decision.
Also, with all the positive buzz there once was about Carnes, I find it hard to believe he could not adequately fill the #2 role at this point in time. The stuff about Armstrong now, that is (sorta) where Carnes was a season or two ago. The main difference IMO being that saying such positive things about Carnes were a challenge to Taylor and as a result less welcome, whereas Armstrong has some safe distance between his and Taylor's hypothetical starting era.
I agree with a lot of this. Regarding the bold, Carnes would have to nearly be a washout at this point if it's true, and I don't believe it is.
Also, if you catch glimpses of Carnes on practice film he looks like he's added quite a bit of muscle in the last year. Last time I saw him, which was, admittedly just under a year ago, he was tremendously thin, like WR thin. He looks bigger now.