FFF:
The Seneca 1 has a 13kt max demo'd xwind and at this XWC the last part of the approach (rudder to align, wing-down for zero drift) requires huge amounts of rudder and aileron input (getting near to full deflection). Obviously power on the upwind engine helps if the runway isn't limiting, as does a little crab.
You're correct that there's an aileron-rudder interconnect (because of the low roll response at low speed and the adverse aileron yaw) but I assume this uses a spring; it certainly doesn't limit the ability to use the aileron/rudder independantly.
VFE:
A limit based on wing lifting due to a xwind is a little difficult to swallow. Admittedly the secondary effects of sideslip in a zero-crab approach lead to a downwind roll (which needs to be countered with aileron) but the aileron response depends totally on forward airspeed. On the ground a pure crosswind will only cause wing lifting once a wing starts to lift and the ailerons will not have any effect because of the low or zero airflow over the wing.
Can you explain your theory a little more?
HFD