Here are a couple ideas for a what-if scenario where i wrote the HP books, same universe but different author

 

1. Instead of trying to kill Harry, Voldemort 'adopts' him and decides to train him himself because he doesn't want Harry to be influenced by muggle-lovers

 

2. in my story, Harry is an anti-hero

 

3. sometime during the beginning of the first book, Harry discovers that Voldemort has lied to him his entire life and comes across Dumbledore and he signs him up to Hogwarts where he is not really liked by most students, and he is admitted to Slytherin

 

4. The first book would be about Harry trying to stand up and convince other people by saying ''Hey, look, my adopted dad may have been a dick that kills people but i am not like him!'' 

That's unreasonable. Voldemort believed that Harry would kill him one day, and wouldn't have given him a chance to live, whether he was under his influence or not. And, if he had instead gone after Neville, then a whole lot more would be different.

I rather not change the Harry Potter series at all.