you can't legally use GPS as a primary mode of navigation anyway
Would you care to provide a reference to substantiate that? As far as I recall, the last time this was discussed the regulations were found to say something along the lines of "suitable form of navigation equipment" and made no mention of the word "chart" whatsoever. As such, providing your GPS can alert you to danger zones, airspace boundaries, obstacles etc it fulfils these criteria. Not only that, but you are in the driving seat when it comes to updating which means you don't have to wait anything more than a month to get a new database.
Most of my primary nav is done using GPS, although I find a chart much easier for at-a-glance airspace recognition, especially in highly segmented areas with different CTA bottoms.