Surprisingly almost like canon. He'd have a different approach and attitude with replacing the soul king.  He'd still experiment on hollowfication as a way to get stronger and fight the royal guard. Once he meets Ichigo in the soul society arc, he'd be transparent with him and it's not just Gin and Kaname, but a few more captains joining him. It's basically a secret civil war. Once they all retreat to Hueco Mundo and prepare for the actual war, it's just Yamamoto and loyalist to the nobles with majority of the captains siding with Aizen. Aizen actually succeeds in this as he'd have Ichigo with him and they won't kill anyone for this. Some Espadas might die but that's it. There'd be less casualties.