Wouter,
I am not talking about your fantasie system. I'm talking about the real world systems being discussed on the forum, hardware that has been built and tried and in production.
The straight track produces the greatest change in leech tension for an inch change in car position along the track for reasons of geometry. The curved track bent to the radius of the foot of the jib produces no change in leech tension for any and all movements of the traveller car. For this reason this set up requires an additional control line to set the position of the jib car along the track. Jib tracks bent to a radius less than the straight track but greater than the jib foot radius have various gradients of jib leech tension change for a given amount of car movement along the track. For example, a track bent on a radius only slightly greater than the foot length of the jib will move the jib car along the track a large amount for a small change in wind pressure and leech tension change. On the other hand a car running on a straight track will move very little for the same change in wind pressure and leech tension.
I'm not saying what is good or bad here. I'm just trying to explain the nature of the beast.
Bill