Finally got around to watching the eighteenth ep of the second season of Arrow just now and I gotta say, I'm really digging how Slade Wilson is going after Oliver via mind games and manipulation, rather than just going directly at him. Case in point, in "Deathstroke", he kidnaps Thea, Oliver's sister and through this, tricks Ollie into making (albeit temporary) Isabel Rochev CEO of Queen Consolidated, who as it turns out, is working for Slade. She then seizes control by having the board of directors make her the permanent CEO. This lets them to focus the company's applied science division resources on replicating the Mirakuru serum running through his veins. It's also revealed at the end of the episode that the kidnapping was merely a distraction so that Slade could hijack a prison bus and recruit soldiers for his army.
Another bit of manipulation was when he released Thea and told her that Malcolm Merlyn was her biological father and that Ollie knew. I'm not sure if Roy leaving Starling City at the end of the ep was part of his plan too, but if I were him, I would say it was. Getting Quentin Lance arrested for aiding Arrow obviously was part of his plan and plays into his visit to Laurel, where he reveals Arrow's secret identity to her. My guess is that he wants her to use that bit of information as a bargaining chip to get her dad off the hook, or at least make Ollie think that she might.
My guess is that this is all part of a big distraction so that he can create an army of Mirakuru enhanced foot soldiers. He promised Sebastian Blood control of Starling City and such an army would be more than enough to do just that and more. His revenge against Oliver is just icing on the cake, a bonus.
Of course, it might not be about taking over the city. Maybe Slade is taking a page from Bane's playbook and trying to break Ollie down before moving in for the kill. He's already going after him psychologically and maybe he plans on using his army to wear Ollie down physically, like Bane did in Knightfall. Either way, I'm really digging where this is going.