If I recall correctly, there once was no sensor limit. It caused serious lag issues when someone tried to push the sensor range *really* high to see the whole, or most of the, map. At least it caused that one guy serious issues. It might have been a PC problem, as my PC is powerful and doesn't have lag issues when I try to distribute sensor ships everywhere.
Yes, a sensor range of 15 can be a pain, especially when ships are running around with speeds greater than 15. I don't think there is anyway to remove this cap.
