There’s a light next to where i used to live that, like you suggested, used the flashing to indicate when right turns were allowed. I liked it especially since there was a lot of pedestrian traffic during the day but basically none at night (and was thus able to handle the different needs of the road depending on time of day), and it was a really intuitive way to let drivers know what the pedestrian signals were doing. Best part was it was for a right-turn-only lane, and had flashing-yellow (no green at all) to remind you to check for pedestrians and bikes.