Ooh, this is interesting. Some things to chew on:
As an adept(us), Harry's countermagic would prevent him from using his wand effectively...but he can still do potions. What about other forms of inherent magic? Can he still use a broom? Apparate? What happens when he touches a portkey, or uses floo-powder? Not that these questions need to be answered now (except perhaps the broom, that's important if he's going to continue as Gryf's Keeper).
Astral Perception/Asensing/Mage sight - I think that this could be done well if it's kept at, or below, the level of ability that Dumbledore shows at this. Basically, he becomes good at spotting things that have been touched by magic, and perhaps in figuring out what they do, eventually (it takes time to learn that trick, and time to use it as well). For the most part, if he could do it at all, it would just be that enchanted or magically active objects 'stand out' more, or in some other way become more prominent and detailed. It's a better way of visualizing (and breaks canon less) than having him peer into another world.
Mind Magic - To keep with the 'Harry annoys snape by being a prodigy in weird subjects' trend going, and because it is fitting to someone with inherent countermagic, Harry should be a natural prodigy at Occlumens. This effectively eliminates the 'Voldemort's plotting make's Harry's scar hurt' plot device, but it makes sense and could be used in interesting ways in the story. On the other hand, Legilimens is pretty obviously something that requires the use of a wand...
Aside from that, you're going to need an excuse for why Harry manages to pass his 'casting' based classes, such as Charms and Transfiguration - or he needs to drop these.
Martial arts - Nicholas Flamel was a famous french alchemist. The only European martial art worth a hill of beans is the french Savate. I think it's a match made in heaven.
en.wikipedia.org/wiki/Savate
en.wikipedia.org/wiki/Nicholas_Flamel
"Not this again!" Minerva said. "Albus, it was You-Know-Who, not you, who marked Harry as his equal. There is no possible way that the prophecy could be talking about you!" - Harry Potter and the Method of Rationality, Chapter 84
As an adept(us), Harry's countermagic would prevent him from using his wand effectively...but he can still do potions. What about other forms of inherent magic? Can he still use a broom? Apparate? What happens when he touches a portkey, or uses floo-powder? Not that these questions need to be answered now (except perhaps the broom, that's important if he's going to continue as Gryf's Keeper).
Astral Perception/Asensing/Mage sight - I think that this could be done well if it's kept at, or below, the level of ability that Dumbledore shows at this. Basically, he becomes good at spotting things that have been touched by magic, and perhaps in figuring out what they do, eventually (it takes time to learn that trick, and time to use it as well). For the most part, if he could do it at all, it would just be that enchanted or magically active objects 'stand out' more, or in some other way become more prominent and detailed. It's a better way of visualizing (and breaks canon less) than having him peer into another world.
Mind Magic - To keep with the 'Harry annoys snape by being a prodigy in weird subjects' trend going, and because it is fitting to someone with inherent countermagic, Harry should be a natural prodigy at Occlumens. This effectively eliminates the 'Voldemort's plotting make's Harry's scar hurt' plot device, but it makes sense and could be used in interesting ways in the story. On the other hand, Legilimens is pretty obviously something that requires the use of a wand...
Aside from that, you're going to need an excuse for why Harry manages to pass his 'casting' based classes, such as Charms and Transfiguration - or he needs to drop these.
Martial arts - Nicholas Flamel was a famous french alchemist. The only European martial art worth a hill of beans is the french Savate. I think it's a match made in heaven.
en.wikipedia.org/wiki/Savate
en.wikipedia.org/wiki/Nicholas_Flamel
"Not this again!" Minerva said. "Albus, it was You-Know-Who, not you, who marked Harry as his equal. There is no possible way that the prophecy could be talking about you!" - Harry Potter and the Method of Rationality, Chapter 84