He might get involved in a battle across different galaxies to protect the wizarding world from an intergalactic threat. His power to control space would be crucial in quickly transporting himself and his allies to different battlefronts, and also in creating strategic barriers in space to fend off the enemy.
Well, in such a fanfiction, he might control space through his magic wand. Maybe he uses a special spell that he discovers or invents, which allows him to manipulate the fabric of space, like creating portals or warping distances.
One implication could be a change in his combat abilities. He could use metal objects as weapons or shields more effectively. For instance, he could make a sword fly towards his enemies or create a metal barrier to protect himself.
One consequence could be that he loses the trust of his friends. They might be afraid that he could control them at any time.
Alien races that are envious of the Earth - born magic could be enemies. They might see Harry and the wizards as a threat to their own power and dominance in the universe. Also, there could be dark wizards who have escaped to space to avoid the law on Earth and continue their evil deeds, now with a new set of space - related challenges and opportunities.
One interesting scenario could be Harry using his space - control ability to instantly transport himself and his friends to hidden, safe places during the Death Eater attacks. For example, he could open a spatial portal to a secret forest glade where they can set up a temporary base. Another could be using time control to go back and prevent certain tragedies, like Sirius's death. He might be able to freeze time right before Bellatrix casts the fatal spell and save Sirius.
Often, Voldemort remains the main antagonist. Even if Harry can control space and time, Voldemort's thirst for power and his army of Death Eaters are still major threats. He might try to find ways to counter Harry's new abilities or use them for his own evil purposes. For example, he could try to capture Harry and force him to use his space - time abilities to open portals to places where more dark magic items are hidden.
If Harry uses his space - time control abilities in the fanfiction, he might accidentally create alternate timelines. For example, if he saves a character who was supposed to die, that character could then go on to make different choices that change the entire course of events. This could lead to a situation where the world he knew is no longer the same, and he has to deal with the chaos of these new timelines.
In this fanfiction, Harry could have an adventure of uncovering the true power of Potter Manor. The manor may have been built on a powerful magical ley line, and as Harry explores, he discovers that the manor has the ability to amplify his magic. However, there are also dark forces that want to take over the manor for its power. Harry has to battle these forces while also learning how to harness the manor's power for good. He might also discover a hidden room with a prophecy about his future and the future of the wizarding world, which would set him on a whole new adventure to fulfill or change that prophecy.
He could use his shadow - controlling ability to spy on the bad guys without being noticed. Just like he sends his shadow into their secret meetings, and the bad guys won't detect his presence at all.
One problem could be that it might deviate too much from the original spirit of the Harry Potter series. The series is mainly aimed at a wide audience including children and young adults, and excessive focus on alcohol might not be in line with that. Also, it could give wrong impressions about the wizarding world if not handled carefully.