OBD is not what we plan, ECU´s are seeding the data with a maximum of 1hz over OBD, with that you cannot see overboost or knock during shifting and so on...
its measuring everything what the OBD cannot deliver, like a race computer, with features in the making like boost controler and so on.
But back to the thead 
Im contacting Seeedstudio how they think about making a Mega with the 2560, and hopefully they will make a small batch 
So far i went trough the data sheet and the fuses look identical, i think the bootloader should also work, just the ide needs a new entry in the list with the different chip.
But would be great to get somebody how realy know what he is doing here ;D