I disagree. What this involves is going back into The Avengers and changing the events that happen - or at the very least, the audience's perception of what really happened. Which, whether intentional or not, winds up feeling like the franchise going, "Haha! You felt bad for the guy dying when he wasn't even in harm's way? What an idiot.".
Almost invariably, it would make the audience feel that they had been tricked and manipulated by the movie. And by and large, an audience doesn't like being made fools of; barring specific genres such as mysteries and con/heist films where getting misdirected is the appeal. However, it's safe to say that The Avengers isn't - and wasn't marketed as being - in that genre.
Also, bear in mind that for the average movie-going audience like Cletus and Ann-Marie, they don't know what a Life Model Decoy is. As such, that throwaway line Stark made at the start of the movie would have no significance to them whatsoever and the whole robot clone thing would just feel like it came out of left field. Worse, it sets the tone that it isn't just good enough to watch every single movie set in the MCU, one must also read the comics from which it was based on even - even though it is not in continuity with the movie franchise - in order to catch and understand elements integral to the plot and development. Which is just flat out BAD practice.