Isn't this all a bit hypothetical surely risk of windshear should be mitigated either by delaying takeoff or furthermore if windshear is reported and takeoff is decided TOGA becomes mandatory as stated in FCOM PRO-SUP adverse weather.
Lastly in normal law the notes in the qrh state if no SRS orders set 17.5 or increase to full back if necessary to prevent loss of altitude. The latter being key in a windshear escape. Below 1300' RA if you're in FAC detected shear the alert will be there so why on earth would you pitch down to follow an Op CLB FD order?