I think Void Steed has more promise for Handlock than Zoolock, although it doesn't have much promise in either. In Handlock you already have a big silence target in Twilight Drake, so if you run Void Steed and both Sludge Belchers then you can get your opponent to run out of silences.
There are some auxillary benefits to getting the guy out there as handlock. You can sac pact him after dropping moltens, although that's probably janky, especially since it's a demon so it nombos with Voidcaller for Malganis handlock, which is the main other use for sac pact. You always have the ability to cycle Mortal Coil, that's nice. It can do 1 damage to some minion every turn, that's nice. Most importantly, every time you drop a Sunfury or DoA there will be a little dude to taunt up on one side, and it only takes 1 HP of taunt to block an entire attack.
And there's the PO shadowflame, that too.
Maybe it's a card, but probably not.
Cutpurse got me excited, but then I realized it's a Pint Sized Summoner that can't be a Pint Sized Summoner if you need to trade it with a 3/2, probably not good enough :/