Tiros, I admit your hardwork. I tried it myself long time ago, but I quit since there is no any data available of the MTK controller. Since you did success in modifying the firmware, do you have any tech. data of the MTK controllers such as data sheet or application notes?
For some MTK DVD player controllers, there are DSP units inside the controller, also the firmware blocks might be compressed. But this might not be true for the DVD drive controller. just for reference.
Never found any valuable datasheets either.
A real good starting point is to decompile the 605 AND the 616T and compare them. You can see easily what has been added by MS since the bulk of the code is the same. When your looking at the disassembly pay careful attention for P0, P1, etc. These ports are actual pins on the MTK controller. Also the famous "yellow wire" control signals are likewise. IDE, LED and Eject also. With a little detective work you can narrow down most of the digital I/O pins and thier P assignments.