So what? Being a standard connector made it easy to repair the connector. What more would you want? Implement the ADB ASIC? Why on earth would you have done that instead of licensing from Apple?
That's what API design is so important, and so difficult. By analogy the DIN connector is simply calling convention and ADB the actual function calls.
Now, if you just wanted to hack peripheral hardware at the time, you would have invested in a lot cheaper (expendable) computer with a standard serial / parallel port, so I don't really understand what you are saying.