Hi Jochen, It would be great if we could get more layers available than "just" Google Maps. I don't know if they can all be integrated but here is a list that often provides images for different library (not always but sometime then do).
This can be of great help as most satellite images suffer from deformation, shadows, quality, aged (in some area the environnement change a lot faster than in Europ), season (wet vs dry season in tropical area), etc.
Something that could be (very) interesting is to add OpenTopoMap layer. OpenTopoMap map layer is more useful than GoogleMaps map layer... OpenTopoMap has terrain/hillshade/contours and one of the big advantage is that OpenTopoMap is directly related to OpenStreetMap project and anyone can edit/add some geographical information (very practical for expeditions).