Block protection

Wood protection - As a person who builds a lot of wood structures and have had them go up in flames i think it would be cool to add a 'waxing' of wood elements much like copper. 
Potentially you could 'milk' trees with either a glass bottle or a bucket and cook the bucket in a furnace to get 'tree wax'. This could be applied like bee wax and would then make the wood fire proof. 

While lightning rods can protect wood structures to some degree from lightning, it would still be useful in terms of not having to spam ightning rods all over ones base. It also would protect the structures from fire spreading from unprotected areas. Maybe one could finally turn fireticks back on then.

This type of wax would also make it possible to utilize fire and wood together, making it possible to make cool lightning sources with flames and wood. Or potentially burned down houses, with fire in them. 

Explosion protection - This could be evolved in regards to protecting your buildings against other types of damage, such as creeper explosions or in the nether regarding ghast attacks. Potentially one could add a gunpoweder with the wax to make it 'explosion' based protection.