Manual trim during flight is a very important feature for those who are looking for flight physic realism and use good joysticks and rudder pedals. It allows to make accurate manouvering and mantain a perfect hover, even relaxing during long flights.
Unfortunately for the players that, like me, uses pedals, the trim interests not only the cyclic but also the rudder. This feature could be counterproductive, forcing the player to trim rudder again multiple times after take-off or during the landing to align the helicopter during flight. In this way the pilot looses his central hover position trimmed during hover check. It should be great if, like DCS, you could also trim only cyclic without rudder.
As said before trim could be incredibly useful but in real life the pilot knows the exact position of the trimmed axis. It would be great if Bohemia implement, like in DCS, a simple axes situation monitor that help the player during manouver.

Summarizing I suggest Bohemia some useful features:
1-Implement an other key or a setting to avoid trim the rudder pedals with the cyclic
2-Implement a device axis monitor in game that allow players to know the exact position of the trimmed cyclic (and rudder).