On the stock rom, this would likely involve changing the kernel ramdisk to make the init.rc script and friends map it differently. Since the bootloader/ROM is locked, this is probably not going to happen soon.
The CM10 port, on the other hand, currrently makes the external SD the "default" (due to its Quattrimus/Spectrum heritage that had no internal storage) and mounts the internal storage at "/storage/internal", but the file manager refuses to navigate that directory without root even though it is world writable, so that will probably be changed soon to "/storage/sdcard1" or something similar. Is that more along the lines of what you wanted?