Sableye has better usage with Prankster; that's basically the only reason to use it, especially over Spiritomb.
If you really want to use a Sableye with Stall, there are a few things that give it some viability, like Assault Vest and Shadow Sneak.
Sableye @ Assault Vest
EVs: 252 Atk, 252 HP, 4 Sp. Def
- Power-Up Punch
- Shadow Sneak
- Knock Off
It'd be an interesting set to use, and has the added bonus of the element of surprise. I would add that you should really only use this set if your Sableye has max IVs in HP/Atk/Def/Sp. Def, otherwise it has little chance of surviving more than 2 hits, even with Assault Vest.