This is what I believe the key attributes would be for such an upgrade.
- Ability to trigger the whistle and bell from the command remote.
- Engine sounds variable based on motor speed.
Another issue that I'm not sure how it would be handled is getting the board out of reset at power up. It's never been clear to me if the low voltage startup is handled on the bottom or top board. Since command comes up at 18 volts typically, the combo would have to come up running without starting at 10 volts or less.
