You can always still reduce to VLS but lose the manoeuvring margins
Where did you find this? The so-called margin you speak about is significantly different at S and F speed respectively. Many companies recommend against/restrict their pilots to fly below GD, F, S, however the aircraft can be flow between Vls and Vmax anytime. (example: V2+10 is a lot lower than S speed on an 1+F takeoff)
Also I wouldn't call S and F maneuvering speeds as they do not share the same characteristics as GD and do not have any fixed relationship to Vs1g or equally Vls and as such do not represent specific points on the L/D curve.
S and F speed are minimum slat/flap retractionspeeds! Airbus chose them as managed speed targets during deceleration because of the simple fact that they will always be between Vls and Vmax; so flyable.
Doesn't Airbus Industrie only talk about maneuvering margin (max bank) in the OneEngineInop case? The AEO scenario vs. max bank below S,F,GD remains untouched by Airbus.
Anyway these are my thoughts. Would appreciate any input.