Okay then, how about this.
Keep the basics of the rules the same. Just judge how the material will react to things differently - start a chart and keep it for later reference as they come up.
Fire
Paper Scrolls: will burn
Rock Scrolls: will not burn
Weight
Paper Scrolls: light
Rock Scrolls: <assign a semi-standard weight here>
Mallability
Paper Scrolls: can be rolled up for easy storage
Rock Scrolls: solid
Hardness /hit points
Paper Scrolls: have a hardness / hp of (whatever in the book)
Rock Scrolls: have better hardness / hp ratings
Water
Paper Scrolls: ink and paper eventually get ruined
Rock Scolls: engraved carvings remain regardless of weather conditions
So, basically, with paper scrolls you have some ease in transportation. But if you are willing to give that up, you have a rock scroll that is more durable (but weighs much more).
If you play the pros / cons of one type, be sure to play both the pros / cons of the other type.
just my thoughts (and I like the idea by the way - I don't think I've said that yet

)