So, um, just reading through the Bios, and I'm wondering if I'm having an accurate view of your line of thought here:
"Oh, Molzapart really sucks. It's a childish creation with basis in shameful ideas of Pokémon hybrids and legendary-Pokémon-of-slightly-more-oomph. I guess I should get rid of him. …And replace him with this uncalled for bastard lovechild of Azelf and a Luxray! I'm so smart!"
…otherwise, I do love that fic you're running.
You seem to be implying that Mementity is not an improvement over Molzapart, which is simply false. Molzapart is bad because he is silly and out of nowhere, his existence does not make any sense, and he has powers there is absolutely no remotely logical reason he ought to have. Mementity, on the other hand, fits in with the other legendary Pokémon, has a natural reason to have memory modification abilities, and integrates sensibly into the general backstory of the fic.
As for being a bastard lovechild of Azelf and a Luxray, she simply looks how a fourth member of the lake trio might sensibly look. Of course she looks like Azelf; they all look like Azelf. Luxray does not come into it anywhere and merely happens to have a similar color scheme and a spiky head that looks vaguely similar from this perspective.