If the fairing is ABS then properly repaired it will be stronger than before. From the inside where it isn't visible you can plastic weld an ABS patch if you feel the need.
You don't need to use fiberglass or epoxy. You should be careful not to make one area of the fairing more rigid than before or you can create stresses elsewhere and create a bigger problem down the road.
Many OEM fairings of days past were actually resin, not ABS so check because many plastics and resins are not compatible with each other.
If it is truly ABS, that is good news as repair is straight forward.
Be very careful using solvent to make the repairs. The solvent weakens the ABS and if you use too much the surrounding ABS is softened and then hardened but much weaker than it was before. The best way is to introduce solvent with a syringe into cracks and brace until cured which takes a minute or less for the initial set. Wait 24 hours and then proceed with any patching or other strengthening efforts.
Do not use solvents or epoxies to make the area stronger. ABS must flex and epoxies and fiberglass won't like the ABS. Use 3M 560 and ABS to patch from inside. The result will last forever and remain flexible without wobble or too much flex. You are seeking a balance and the procedure outlines gives you that.
Good luck.
