The Tech Prince of Britannia

Before I went to hell I was offered a chance to live in one of my favorite worlds as long as I help the collective consciousness of humanity to not be destroyed by the Emperor. Well, at least I get two wishes before going. Now, how will this world behave when someone with unprecedented intelligence enters the stage? (SI-OC, mechas and other techs from other animes, AU with time, Harem accepting suggestions...