I looked at the remaining gym leaders plus what Poke's are available, and found a few ideal hole-fillers, namely Scraggy/Scrafty and either Onix/Steelix or the Rhyhorn line. Fighting/Dark will sweep two gym leaders, and Rock/Ground or Steel/Ground will provide the anti-flying anti-electric gap, which is the only coverage i'm missing after the Fennekin line (Fire/Psychic), Fletchling line (Fire/Flying), Bulbasaur line (Grass/Poison), and Azurill line (Water/Fairy)
Since Fletchling has a fire redundancy, though, i may look for an interim flying type to fill the gap. Endgame, of course, the flyer will be Yveltal.
Monster Hunter: pissing me off since 2010.