PVC piping for low-pressure air line?
Would applying a safety factor to the maximum PSI in the PVC lines allow me to safely use PVC?

Yes it probably would, as long as this is a personal project at your home or property. If this is in a workplace then it is likely you would be breaking the law by using unprotected PVC. 

I would regulate it to no more than what is necessary to provide desirable results and set over-pressure protection at that setting as well. Also affecting safe use are factors such as UV degradation of the plastic (by sunlight and/or artificial light), placement where it could be struck/damaged while in use, etc. ANSI says max pressure is 100 psi, and that's for underground systems and above ground systems that are "protected".