James
I reckon if we wanted to make a setup change mid race(if it went wet/dry or dry/wet), on the pit screen where it says what tyre you're pitting on, how much fuel you put in your next stint and laps of fuel left we could have a 'change setup' box where you can adjust the wing levels only. I've seen this in f1 races where the pit crew adjust the wing levels of the car. If you wanted to change the wing levels though it will add a little time to your pit stop(around a second)
Makes sense during a rain race. Otherwise just if there ain't a real ideal setup that you can set before the race, but it rather shows you a range where it tells you that you're now in the ideal setup range. But you can't determine it further and have to do the last research on track what is now the best setup within that range*. Maybe even drivers with a higher knowledge giving you a more accurate range or a probability that this setup is the ideal setup (the number you tested in the practise session, e.g. ride height: 22 prob. 82%, wing level: 20 prob. 85% in Monaco). One could even implement that the ideal setup changes every season within that range in order to fight monotony. Or they have to implement that the ideal setup can change during the race.
*E.g. Monaco: ideal ride height range: 20-24 instead of ideal setup 22, ideal wing level range: 18-22 instead of 20. The values change a bit between drivers, but that's what is mentioned in Joey McLane's advanced guide.