it's worth mentioning again how the 787 might behave in this particular scenario
It will behave better. A short and intensive fire is better contained/survived by gradually burning composites than by spontaniously melting aluminum. If a fire burns longer, toxic products from the hot inner surface may become a serious issue, but actual penetration resistance should still be higher.
If you want to be really safe, fly the A380 and sit in an area where the fuselage is made from Glare, it meets the criteria required for firewalls...