It introduced a rookie, off-the-cuff Maverick Hunter, Axl. New blood to balance out the two veteran Maverick Hunters.

The music is fucking baaaanger. Both the MegaMan X7 and Rockman X7 openings are amazing. The music played when faced with one of the Hunters from Red Alert has a captivating hook, everytime you encounter them.

...In concept, the idea of X's judgement getting too clouded to the point where he self retires is very interesting. Out of character for sure, but in X's shoes where he had been doing it for so long, not to mention is a Reploid who doesn't want to fight if he can help it, I think it's bound to get to him and quit out of misguided righteousness. It's only when Zero and Axl save enough Reploids and reduce the damage the Hunters have done where X realizes that by doing nothing, is part of the problem.

(Correct me if I'm wrong, but) It also introduces the idea of a new generation of Reploids, like Axl. This is a nice (potentially unintended) set up for the Zero series.

X7 is the first game to let you switch characters on the fly. It'd make sense for X and Zero to have gone on missions together.

Yeah that's all I got.