How can I create offline maps with more than 500 MB?

I have enough space on my SD card and also WIFI with high transmission rate. I would like to create maps (especially Google maps which is not available at Mobac) having high zoom level which have some Gigabytes.
However there is the limitation of 500 MB. Is there a possibility to change this limit?
Or would it be possible to download some different maps (with different zoom levels) and then combine them. I would like to have Google Maps up to zoom level 12 for whole Germany and then I would like to have some selected regions with zoom level 13-16. I can load all these maps but when changing the zoom level from 12-> 13 I need to select a map (I use also OSM maps for hiking and biking). It would be nice, if Oruxmaps would continue with the same map source (Google) when I increase the zoom level from 12 to 13 and also decrease from 13->12.

Best Regards!