Did a really quick little project last night. I'd been kicking this around in my head but decided to try it finally last night. The M.O.D.E. or Multi-Optical-Disc-Emulator from TerraOnion has a nifty set of additional pins along one side of it for adding in additional features. Among them are the ability to add in a wire for adding a physical reset button or button to simulate a Disc Swap process etc. One of the extra pins is for wiring in an additional LED in the system somewhere that is directly tied to the small SMD access LED on the M.O.D.E.'s PCB itself. Because this LED isn't usually visible with all inside the case of the console it makes sense that they would provide such a pin. I'm sure it was intended for an additional LED but I decided to instead change the actual power on LED on my Dreamcast to act as the access LED. This way, it still serves as a power on indicator when you see it blinking with 'disc' access activity taking place.
The way I did this wasn't difficult at all. I simply removed the power LED from the controller board. Reformed the + lead on the LED to be 90 degrees pointing toward the back of the DC when reinstalled. From that reformed lead, I soldered on about a foot of wire to it. That wire in turn would connect to the LED pin on the M.O.D.E.. I then soldered the power LED back in place on the controller board only soldering in the - or ground lead in place. This way, when the system is powered on and in use, the + voltage to feed the LED and light it up will come from the M.O.D.E. during disc access activity indications. Again this isn't difficult at all and I did add shrink tubing off my + lead and soldered wire to ensure no shorts would occur around the controller board. But here is an edited video example I took off my phone showing how it looks.