Risky to say the least. 2 reasons.
1/ If the A/C is braked using wheel brakes, then the chances of it sitting on it's a**** are high.
2/ When reverse is used at low speeds or stationary, then the risk of injestion, therefore FOD damage is high.
The crew will not know the extent of this damage untill the engines are stationary and a visual inspection of the 1st stage fan is carried out.