The thing is, it seems to only use it due to being a hedgehog.
I really don't like the idea of a second triangle. Even if it's Grass/Fighting, Fire/Psychic and Water/Dark, like you want.
Actually, I'd love that too, all three are decent-ish typings.
However, what really makes me weary is;
a), GF is never this obvious about starter final typings, yet Fennekin seems to be.
b), He had to correct it.
c), He provided no other detail about them.
Plus, Hariboogu/Burigaron and Mafokushii/Teeruna makes me think Grass/Steel and Fire/Fairy, mostly because of the armour (usually made out of Steel) theme and magic/moon, both of which seem to be related (not strictly to, but related) to Fairy. Gekkogashira and Gekkouga, which seem to be Gecko + Boss and Ninja each, make me think Dark-Type, too.
Wait a minute! Steel, Fairy and Dark? Those three are all the types that weren't in the original fifteen! And Pokémon with those types are generally given lots of attention...