What would be a good idea, at least while the cars are on the 7, is to have an easier way to quickly distinguish between local and express on the side signs.
Doesn't really matter much to me since I board and get off at stops where it doesn't matter, but I'm always able to see whether its a or a just by looking at the LEDs. On the 142/a one has to actually watch the side sign change readings to figure out if its a local or express, and those few seconds can make a difference in making or missing the train.
Perhaps a new service number would easily take care of that if the display isn't modified to show circles and diamonds, since the number is easily visible.
Disclaimer: I know this probably won't get done because of cost issues, but just an idea.