An optimized v1 for a slippery runway take off comes lower than v1mcg what must happen

This is because V1 must never be less than V1MCG (Minimum Control Speed on the Ground). If V1 were lower than V1MCG, an engine failure at V1 would mean the aircraft would not have sufficient aerodynamic control to maintain directional control on the runway, potentially leading to a runway excursion during an aborted takeoff. Therefore, the takeoff decision speed (V1) must be adjusted upwards to meet the V1MCG constraint, even if it means a longer accelerate-stop distance or other performance adjustments.