I think that fire should be able to spread more realistically:
-If fire is 5 blocks away from a tree, the tree should start burning.
-There should also be some sort of a fire resistent suit that you could make.
-A special mob: THE FIREMAN.... he stops all the fires within a certain range.
-Fire fighting equipment.
Hazemat suits/fireproof suits are quite modern
Firefighting equipment is quite modern too, people used water before.
What would be the point of adding a mob that helps you without doing anything for it.
i ment that you could craft him, like the castle defender mod