Alternative suggestion: Instead of hardening it, increase its range. Helps with setting up a defence in a timely manner.
At the same time, to even things out and to make it fit to the WW2 theme: Decrease precision, accuracy, detail, and timeliness of what it shows. That is, randomize aircraft positions, delayed by a few minutes, and do not show heading or type for enemy aircraft. Make it unusable as in-flight intercept path calculation device.
(to fool those with 2nd accounts, add .transponder off/on/alt allowing each player to select how to be shown to countrymen, where "off" is shown as blurred as enemy, "on" shown as currently, and "alt" adding altitude to the mouse-over.)