The problem of planes feeling underpowered may be a by-product of lack of perception when aircraft is being stressed. You pull the aircraft to it's limits and it falls off the sky with little warning.
We need to hear a more pronounced airflow noise change from inside the cockpit along with some shuddering, and changes to the contrails, some axis tuning (you get maximum input with little deflection), things like this that also add to immersion. :)