Modding UT4 with different physics?

I've heard it is hard to change the movement physics using unrealscript or that fancy-pants blueprint system. I would expect you could quite easily implement the rudimentariness in C++ on there though. I've not seen any example of such movement yet however in UT4/mods/games using the engine.

It could be that many things would need to be rewritten at a deeper level? I don't know, I have no direct experience with the engine.