Hey rennerskt, sure you can erase the patches, although you may want to save to PC, or write down the other patches, hey you may like them, worth saving IMHO (try them before you dump them
).
Others correct me if I'm wrong, but I think you'd have to zero each other patch (>69 then save that (individually) to erase them ? but that will work) Maybe you just take out/disconnect the memory battery to dump everything ? (although I think factory patches load from firmware ?) MJMP will have the good oil on this BTW.
But yeah you can take it back to basics one way or other and build from there. You can edit any preset/patch and save it (zeroed or otherwise programmed). If you want a quick way, I suspect the battery disconnect option may work ? Factory sounds will load from EPROM.