Quilava is more badger than hedgehog or echidna to me.
As I am the one suggesting the Mongolian Deathworm, it should be up to me to justify it.
I am by no means an artist, but the mental image I have of this thing is a mongolian deathworm with some graboid (Tremors) and sandworm (Dune) mixed in. The sandworm teeth part wasn't a joke - if our fat red earthworm possesses a
mouthful of teeth dripping with venom, we have Spikes or Toxic Spikes (And maybe Crunch, for those afraid of the Psychic weakness, getting down Gengar and the brittle Psychic types alike) justified already. Most snake/wormlike Pokemon (And even Shuckle) get access to Knock Off, so that's that as well.
Electric will be a "secondary" feature - we're focusing on the "earthworm" (Ground) and "incredibly poisonous" (Poison) aspects of the worm. However, like Charizard gets Dragon Dance and other Dragon moves due to its draconic appearance, we can use this to give the sandworm Electric moves - notably, Thunder Wave, and perhaps even Thunderbolt and Discharge to scare off Gyarados as a pleasant extra, or Reflect and Light Screen Electric types usually have.
Gravity and Trick Room will be a matter of flavor, as is Me First - do not forget this move, my friends, our Poison type will likely be fast. Magic Coat is feasible given the slime coat associated with worms. Rapid Spin is a bit trickier, but we can get away with it.
Encore, Wish, Heal Bell, Aromatheraphy, Psycho Shift and Perish Song are likely out of question, so take that in account as well.