It's an interesting idea. When talking about triggering over a certain threshold before the clutch is engaged, I'm guessing you mean detecting the hand throttl

It's an interesting idea. When talking about triggering over a certain threshold before the clutch is engaged, I'm guessing you mean detecting the hand throttle being let go particularly quickly after a downshift blip? I don't have any real evidence for this, but based on how I think I use the throttle when riding, I feel like this would have a very high false positive rate unless you're deliberately using the throttle very gently in normal riding; or a high false negative rate if you tune it so it only activates on really aggressive throttle blips. It would probably be more reliable to just trigger off high vacuum once the clutch has engaged. Also, I'm not 100% sure but I don't think my bike has any vacuum tubing you could tap into - it doesn't have a vacuum brake servo like a car. So you'd have to drill into the intake manifold to mount a sensor.