[IvanK]

"Remember I am not proposing really auto trim: I am proposing triggering the trim action at a speed of change equivalent to a real life trim wheel;
- if you stop pushing the button, the A/C will not be completely trimmed,
- if you change the attitude of the A/C during trimming, the A/C will not be correctly trimmed and you will have to do it again (= releasing the button and push it again) "

In my CH setup with elevator trim set to the Coolie hat (emulating typical real world setups) it already works exactly like that.
You can Blip trim (as is the typical pilot action in most electric setups irl) or if you feel the need just hold the coolie hat switch down for as long as you dare. Not forgetting that even in WWII some aircraft had electric switch activated elevator trim ... the Fw190 series for example.

Now if YOU choose to map your trim to a slider then IL2 behaves exactly as it should emulating a manual trim wheel.i.e the rate and degree of trim is directly proportional to your slider input. Stop the slider and trim input stops... thats how it works on manual trim wheels.

So the system existing in game right now is flexible. It gives the USER the option to emulate manual trim wheels (map trim to a slider) or electric activated switch trim (map trim to a switch). What it doesn't emulate is the spring trim button system employed in some some sailpanes ... and neither should it.

I also see little reason for change what we have works just fine.