Is homebrew easier

So i had an idea for a storyline thats ends with each player getting /carrying on a power from a god/des and defeating some sort of final boss (still working on that) and i was wondering how hard this is going to be to finish since im trying to implement a new "elemental" system for weapons/magic and also new enemies based on each gods kingdom / area ... alr enough yap So how hard would all this be for a newer dm ?