Bit of an odd question, maybe..... My other half has PN (too much riding on a specific saddle 3 years ago). He used an infinity saddle (imported from USA) which kept him riding but for reduced periods of time. He aggravated the nerve last year and hasn't ridden since. He's not a fan of the noseless saddles, plus he's not convinced they'll make a difference.
Someone talked about these elliptigo bikes that you can ride off road but are saddle-less. You're basically peddling standing up (think a bicycle version of a trails bike, sort of!). They look a little bit like a mtb (as in the frame) but are odd. Anyone heard of them or tried them? I know it's not going to be nowhere near the same as riding a mtb but, if this gets him back out in some way, surely it's got to be worth a shot?
There are a few enthusiasts who regularly ride (or should that be run?) Audax events on them, including very long distance events like LEL. If you search YouTube for "Audax Elliptigo" you'll find lots of videos. I see a few videos of them being used off road as well. I guess the main limitation is that they are going to be slower and won't handle such extreme terrain because of the small wheels and the pedalling mechanism.
People who have problems using a conventional saddle sometimes opt for recumbent cycles, so that might be another option to consider.
Was going to suggest searching Audax groups - not seen much about them off road though.
I met a chap using a noseless saddle today. He said it was great. I cannot see the issue with using them as even on a conventional saddle all your weight should be going thru the sit bones
the one he had was just two oval pads that could be adjusted for width apart as well