for sure, we can write software that will let the gp2x format the card itself .. but there is a bit of a delay in these sorts of apps while we wait for the next firmware release; it will be easier to ensure the longer-term safety and 'ease of use' of such apps as a 'card formatter' once we get a stable firmware/source-code pair release ..
just: have patience. i myself am working on a small suite of admin tools for the gp2x which will let you mount/unmount/format SD cards, load modules from SD, unload modules, do some regular system maintenance-style checks, etc. just have patience.