New Maplestory Elements?

I think it's too late to add in new elements to the game. You can't just stuff in another mage class. You would also need to create training spots good for that class. Creating an entire sub-class would be possible but that potential was used for pirates and cygnus which don't stray far from the original classes, but the map problems would still remain anyway.

Keep in mind that a new class was deemed "too much" for the game. A few dark-magic-weak monsters wouldn't be hard to add; have a church-like town and spawn angels or the like around it.