Ok, forget about usb-core etc... since you said that at startup you are told:
mounting USB filesystem succeeded
initializing USB HID interface (usb-uhci) suceeded
initializing usb keyboard succeeded
initializing usb mouse succeeded
Which means all these steps are already done for you.
Now, thr problem seems to be that your keyboard is a file in /dev just for simplicity i will assume its /dev/usbkey (BUT its not, i dont know what it is, you will have to find this out somehow, perhaps look through /proc/usb) and the normal keyboard is /dev/key (and again its not, im only explaining it, you will need to find out what normal keyboard is, maybe some user will know to tell, but i dont) now what you have to do is symlink (ln -s) /dev/usbkey to /dev/key to make your system think that your usb keyboard is the normal keyboard.
Things you need to do:
1. Find out what /dev/file is your usb keyboard represented by
2. Find out what /dev/file are normal keyboards represented by
3. Symlink usb keyboard /dev file to normal keyboard /dev file
Now, i have never done something like this before, which means i might be totally wrong, but that is the only thing that came to my mind. It's kinda like a blindman leading a blindman, so i suggest wait to see if someone else can give you a better answer before following what i said.
Sorry i couldnt give you a clear answer... but i tried