Like this. The very poorly drawn circles are the diodes as they already are, the amber window would be wired to a separate power wire that could be turns only. Could even do it 2 rows and 2 rows, but I feel like brakes are more important than turns and amber usually stands out above red so I don't think as much would be needed.
Like I said though, it's not something that exists (that I've found) and it's probably not worth making a one-off product when very few would want to do the mods to make it work (would need to split the turn signals from the brakes at the turn signal switch, and then use the third brake signal to power all three brake lights. And would need a trailer converter for towing. It's really just me idealizing, I doubt anything like this will ever happen.
If something like this were to occur, I would probably run 2 amber upper side markers (turn only) and 2 lower red side markers (running lamp only, no brake).
