I really like your twist on cannon and in some ways hope you don't make Ron Harry's friend. Cannon Harry had latched onto Ron as the first kid his age who was kind to him but after two years with Pim Harry has self confidence and doesn't need to put up with Ron's jealousy and bigotry...unless Ron can grow out of it, but I just don't see that happening in a young Ron.
As for Hermione I can see a friendship growing if she apologizes about assumptions and realizes that Harry may not be what is portrayed in books or an extension of herself and maybe learning some discretion about where to talk. I cannot see him getting along with a extremely bossy fandom Hermione...shudders...after all he put up with being bossed around for eight years by his cousin and wouldn't want to encourage that in a friend.
I have to tell you I love Pim and his innovation and forward thinking. Can't wait for him to meet Dumbledore. Will you have Harry learn Occulmency? As for Snape I hope you find an excuse to mellow him, I always thought that if he really loved Lily he never would have treated her son that way no matter how he looked like James. Maybe pointing out he is now the over grown bully picking on all the kids?
Anyways thanks for a lovely story and hope you will continue it soon.