By "doable", you mean to correct the model ID after conversion as discussed in posts from #5, then i agree that quite likely, if it's fw based, it can be done but i don't know how. You clearly have the motivation, so if you also have some coding experience and lots of time to investigate and the key is contained solely in the device firmware, then it is doable. However, because it's reputed to be a 'closed shop', Garmin's proprietary operating system is not known to be modifiable like Linux-type systems on which it's distantly based. So, if rather than fw the key to changing the model ID is buried in the actual OS it's a probably a waste of time to try.

You say "I know for sure it's doable". How do you know that?