I really appreciated the change, a number of years ago, when IPMS dropped the plastic content rule. I do a lot of scratch building, and always chose my materials based on what material was best for each part, so all my scratch models were multi-media.
My favorite scratch material is wood. I began modeling in the BP days (before plastic) when solid models (the term at that time for non-flying scale models) were made of wood. The kits usually included the fuselage sawn to profile, and some even sawn to planform too. Only a few really deluxe kits had machine carved fuselages carved to section also.
As far as paper, anyone remember the Joe Ott kits, that had pine stripwood, with die-cut cardboard for ribs and fuselage formers? There was another line of kits, forget the brand, where you laminated fuselage and wings from die-cut thick cardboard. You then painted it with several coats of thinned shellac to harden surfaces so you could sand the steps away.