Not my solution, it is a Boeing recommendation and an Airbus Golden Rule to call out FMA changes and in every SOP I have seen, so nothing radical in my post at all.
So, given that it is pretty much standard practice for FMA changes, surely it is reasonable that the principle extends to any other change in aircraft state actioned not in response to a request or by the aircraft itself.
Never having flown an Airbus (currently on the E145), I can't make a specific comment. However, what's the point of calling out normal, expected reactions to MCP input? At my company, the only FMA callouts are when an unusual mode change has happened. Even so, we're not expressly told to make a callout, we just do. Common sense, I think.
If we're going to call out the expected result of a normal input, why stop at the MCP/FMA? Why isn't there a "rotating" call as the nose leaves the ground? Wouldn't it also be beneficial to have the PF call "idle power" during the flare, then have the PM aurally verify that the engines are spooling down?
How do people find time to listen to ATC with all these callouts being made?