Hermione might be the one. She is Harry's best friend and has always been quite persuasive. She could try to convince him that marriage doesn't have to mean losing his freedom but rather gaining a partner to share his life with.
I think Harry and Blake could also be paired well. Blake's intelligence and her past experiences with the White Fang could be complemented by Harry's knowledge of fighting dark forces. They could bond over their shared experiences of fighting against those who want to bring harm and chaos, whether it's the Grimm in Remnant or Voldemort in the wizarding world.
Neville Longbottom could be a likely candidate. He has shown great courage and has been through a lot. If the situation was dire enough, Harry might train him to be a more effective fighter, bordering on a killer, to protect Hogwarts and the wizarding world.
One great fanfiction could be where they have a magical wedding at Hogwarts. All their friends from different houses come together to celebrate. The ceremony might include spells that create beautiful flower arrangements in mid - air and a Patronus choir. Ginny would look stunning in a traditional white wizarding dress with lace made of unicorn hair, and Harry would be in his best robes.
Harry Potter himself, of course. He has always been at the center of things in the wizarding world. His actions and decisions would likely have a great impact on any change that occurs.
It could be that Dumbledore has some strategic or protective reasons. Maybe the electives Harry chose initially could expose him to greater risks or prevent him from developing crucial skills needed later on.
Clawdeen Wolf might be the one. She's confident and brave, just like Harry. She could see Harry as a kindred spirit. Her fashion sense might also intrigue the Hogwarts students. She would probably befriend Harry and then introduce him to the wild and fun world of Monster High, and in return, Harry could show her the secrets of Hogwarts.
Probably Harry Potter and Indiana Jones themselves. Harry's knowledge of magic and his experience in fighting dark forces could complement Indiana Jones' skills in exploration and combat outside of the magical realm.
Harry Potter himself might be a likely candidate. He has experience in facing life - threatening situations and has a strong sense of justice. His skills with a wand could give him an edge in combat and in finding resources. For instance, he could use the Patronus charm to keep away dangerous creatures in the arena.
Hagrid, of course. He loves all kinds of strange and dangerous creatures. He would be the first to be intrigued by the Indominus Rex and would probably try to approach it to see if he could take care of it or at least understand it better.
Hermione is a very likely candidate. With her intelligence, she could easily start a business. For example, she might open a library - like establishment but with rare and restricted magical books that she has managed to collect through her research. She could charge a membership fee for witches and wizards to access these valuable resources.