This is actually somewhat possible already. You can copy pti_wms.db from .mapsi directory to SD card and then select to use that database file from the settings. Also with Windows version(which will be probably released today) if you have N900 connected in mass storage mode, you can select to use Mapsi database in N900 so all downloaded map tiles will be saved there. I don't have in mind any new major features but I'll probably improve map tile downloading(possibility to download automatically from multiple layes and maybe dividing Finland in regions so that you can download all map tiles from one region and save it to its own database file) and also will do better geocaching support.