I'm trying to come up with a name for the 'gift' humans get when they get their cutie mark.

May it be out of contact with magic like Tyler and Rachel, being harmonized like Sam or out of sheer willpower like Flynn. Since it's an adaptation of the body that is different from case to case and hands out different advantages to the body, I first thought of Meld since magic and human tissue can coexist and do extra stuff.
Then again, nothing is melded together. It's not just a pure enrichment of the body with magic either. Sam and Flynn don't need magic to use their talents, only Tyler and Rachel do so.

The fact that they use Tyler's blood as Energy source for a hover tank comes into play as well.

It's hard to come up with an english term that is likewise broad enough to cover everything and precise enough to get it to the point. Especially if one isn't of english mothertongue.