The bump out or pop out bay window, would have limitations based on the function it preforms. In some cases the bump out is aesthetic only and the interior space has a ledge while the exterior appears to be added space vs. adding of additional square footage. You would need to consult and Engineer and Architect to ensure the appropriate look and feel of the pop out should you be adding it to your existing home. The costs can range significantly based on function and structure and do tend to be pricey. Best, Markay Johnson Construction