Arguing that a capacitor for a craft guitar build is too expensive and technically inferior to a modern PP film cap is a bit like arguing that a wedding ring could have better structural integrity if made out of titanium compared to gold. Personally I prefer using modern film caps to replace bad paper-wax parts in sixty year old Hammond organs, but I could also see why other people would disagree with me on this point.
Anyways, hermetic PIO caps are not that problematic in terms of longevity AFAIK? In my experience, paper-wax capacitors develop leakage due to moisture ingress, and paper-zinc X capacitors are notorious for failing in across-mains applications due to moisture ingress, but hermetic PIO caps shouldn't have any of these issues. A lot of PFC capacitors on the high voltage grid use a PIO construction, with the reliability requirements in this application there can't be anything inherently wrong with the technology. No engineer should use a capacitor without an agency safety rating in an across-the-line or line-ground application anyways, so that shouldn't be an issue with these capacitors.