yeah... I've actually looked into doing that on the TCU on these. It's a Fujitsu MB89665 mask ROM microcontroller. All I need to reverse engineer the firmware is the special programming adapter that makes it look like a 27C256 EPROM to my EPROM burner so I can dump the data out, obviously I would have to buy a new controller and solder it down after burning it but it'd be a start. Problem is, that controller chip is so obsolete I can't find anyone willing to sell me the programming adapter and getting a schematic to make my own is completely out of the question.
I don't know if it's applicable on these, but on the older chrysler ECUs we used to desolder the eprom and replace it with a socket to make changing them easier. The original eprom usually ended up destroyed but it wasn't a big deal as the stock calibration files for different vehicles were pretty easy to find. Of course that's all minor compared to finding a programming adapter.