Currently under cascaded WMS layer, remote requests made by local geoserver to remote geoserver have image format set to PNG and no styles param (which makes remote server use the default styles).
An improvement is proposed in which users under the Published tab can choose what image/format should local geoserver be using when making remote WMS requests. These formats should be fetched from inside Capabilities document. User should be able to enable disable this option through a UI checkbox
Similarly styles attached to remote layer should also be available for user to select as default, so that remote WMS requests can carry user prefference as part of remote WMS request.