I have typically removed the previous owner from any role in which there would be operating decisions and have placed them in either a consultant role for a temporary period of time to assist with the transition until operations have smoothed out post acquisition and integration or have placed them in a position to support future growth leveraging their existing relationships but this depends on a few factors: their desire and transition goals, their skillset, etc.
These decisions are largely due to previous failures around allowing previous owners to have operating decisions and they could never accept the business model shifting the way it needed to and always created friction in the change management processes for operations.
