I think your being overly critical of Rossi's progression. History, and even current history is full of drivers who have had, according to what I am getting from your post, careers which have stalled or even regressed, and yet made a good/decent F1 career (ref. Massa, Grojean). I agree that this past season was not a good one for him as far as results but I think his overall pace and driving skills were better. However, I do not agree at all with you about stalling, at least in the sense that his talent is hindering him. I think it has much more to do with him being an American and not having the money or political backing that European or South American drivers do. He just does not have the available avenues to obtain money that European or South American drivers do. Unless a Bill Gates, T. Boone Pickens, or Warren Buffett suddenly decide to start backing him he's always going to have an uphill battle finding money to run a European series.
As far as reserve driving, I really do not think it matters at all how good the car is. Beat your teammate first and foremost. Then if opportunity arises, provide a unexpected good result (for the car). That is all one could ask for in being a reserve driver for most teams (non Ferrari, RB, McLaren).
I have no delusions about Rossi. He might never drive in F1 GP, and might never win a GP, and most certainly will not ever win a WDC. But I think it's a bit too early to totally write him off, which is kind of what I am gathering from your posts.
