I have watched videos on how to thoroughly clean the firing pin, firing pin springs and firing pin channel of a Bersa Thunder. Just not all that difficult. And it involves removing the safety.
If you have a Dremel tool and an inexpensive assortment of felt buffing attachments and a tube of Flitz metal polish, I am betting one can totally fix the stiff safety. There is a detent in the safety shaft. There is a tiny ball under spring pressure that is under the rear sight, and that little ball goes in and out of that detent in the safety shaft. I am betting that if one were to slighty ramp the sides of that detent and polish it, that the safety would be much easier to work.