all you need to do is look at the eny level in the clipboard country status
While that is true, we have no indicator in the Hanger where you are actually making your choice of aircraft to fly. Additionally, ENY sometimes changes quickly, so whereas it wasn't a problem your last sortie, now it becomes one and you weren't aware of it until you got that message trying to launch.
While only a mild and temporary annoyance, there is another potential benefit. It would give ENY more visability and therefore may help balance sides. The reason is that a lot of the older hands who don't care which side they fly for also tend to fly planes with ENY in the 15-30 range anyway, and aren't affected by it. So, even though they are willing to balance the sides, they may not be aware of the "problem" and that action on their part would be a good thing.
Personally, I'd rather see a message box in the upper right corner with a big number in it if your side is currently ENY restricted, just to make it clear to everyone on that side "hey, you have numbers."