All slalom ski boots or snow board bindings only stretch so far up.
We do want a fix position, so we might want to make the slalom boot higher or snow board binding higher; maybe to almost below the knee.

When riding snowboard the bindings should not rotate but be in a fix x degrees angle.
When kicking the snowboard with the rear foot loose and the front foot fastened the angle should be straight forward (or at another angle).

Why not have a simple manually operated lock/lever that lets the rider loosen the binding to rotate.

Then, when about to ride again, use the same lock/lever to lock the binding in position?