Ethan was 19 when he died, he didn't graduate highschool and suffered from depression but was a good person. He cared for people and hated how people suffered, so being reborn as Ultron he will dedicate his new life to not only trying to make up for the evil acts of Ultron but also to making the lives of some of his favourite heroes better.
Some characters will resemble their MCU selves, others their 616 versions. I'll also introduce multiverse travel and so on later so don't expect anything life that in the early 30 or so chapters.