Look, I really like Japan. And I also really like a bed with a good mattress; futons on the floor are spiritual for some, but not for me.

I believe a stay at a small isolated onsen hotel with western bedding and excellent food (they exist, I stayed at one on my last trip) would be as "spiritual" as any ryokan. And you don't wake up with a backache.

BTW, a lot of the spirituality might vanish if the ryokan was so authentic that it had Japanese style toilets. You ought to check on that.