How did you get your "bumpmap"? Knowing that I can give you a more detailed answear as to whether or not that's a ready "normalmap" to be used in current M&B shaders.
Maybe I should have said height map. A simple black and white one, like this:

I would use the nvidia plugin, but someone said that the native normal maps are green because Armagan's put the red channel in the alpha channel or similar. I'm assuming that the normal maps created with the nvidia plugin won't work because of that.
As for suggestions, you said that Armagan's agreed to allow shaders to be affected by scripts. Can a texture be switched for another one using a script?
I'm mainly thinking of seasons here. If you could switch the grass texture for a snow one, change the tree foliage to appear dead, and make an invisible texture change to make icicles appear, that would go an awful long way to representing seasons in M&B.
And Yoshiboy: Thanks for the link to crazybump. It looks fantastic - downloading now.