I have not modified it to mouse but I suppose it is not difficult to change it. Try to do the following items.
In hidemukbd.c,
1. Change GAP_APPEARE_HID_KEYBOARD to GAP_APPEARE_HID_MOUSE in advData.
2. Change 'H','I','D',' ','K','e','y','b','o','a','r','d' to 'H','I','D',' ','M','o','u','s','e' in scanData.
3. Set hidBootMouseEnabled=TRUE;