Firstly, the general story idea is fairly interesting, so that's a good start.
Now... I will respond to this first:
For the second point, just be sure that it makes sense for Maylee to want to take on gym leaders and has time to do that and it makes sense/is realistic for her to do so in-between 'saving the world' - don't try to rely too much on following the formula of the games after all.
There's a bunch of Pikachu-like Pokemon as well that'd fit that bill; Plusle/Minun spring to mind as does Pachirisu and Emolga from 5th gen in particular. As for non-electric types... well, the list is long! Try some research into it and see what appeals to you to write about; there's the likes of serebii, bulbapedia, etc to use for that.