I can image that programmers think this is too hard, with too little reward.
But if you want to download a new distro/game/video-player for your raspi, and you do not have a card-reader (at hand) then such a utility would be very helpful.
Imagine you are living in a small rural village, and you have to walk 30KM to the next town to buy a SD-card reader. And yes, such remote villages often do have a (wireless) internet connection, in case you are wondering! In even the most remote places they use GSM phones and such.
What about this solution, which might be easier to implement:
At boot time (before loading the kernel), copy the content of the small boot image needed to do this job to a "ram disk", then boot the ram disk, leaving the r-pi's sd-card unused.
As a side issue, (I realize we might have a chicken/egg situation here) I also propose that R-PI distro's use a "boot menu", (similar to those used on live_CD's) that make it possible to choose between booting the three possible memory models (GPU/CPU RAM sizes splits of 32/224 MB, 64/192MB and 128/128MB) maybe with three different (corresponding) distro's, one distro for "full desktops" without multimedia, one for distro's with light multimedia, and one distro (or stand alone application) for running games or other heavy multimedia applications (think XMBC) needing 128MB of GPU RAM. The same bootmenu could then also check if other partitions are present, for example one with this utility, and if present include it in the menu. That way you could partition off small section of the SD-card, fill it with this new (mini) image, then reboot and get the option to run the newly created utility image.