Render and Replace MOGRTs with Alpha

Render and Replace is a great function but appears to only render a full video. It wouyld be great to be able to render and replace a MOGRT so it acts like a finished graphic with alpha, allowing you to still edit the images under the graphic. This would allow the timeline to work much faster and make the system more responsive while editing, but retaining the ability to adjust the parameters of the MOGRT is required.