Our community play lot of PVPs especially combined arms C&H. The current radar system shows the visible vehicles which makes the vehicles very strong. With the current system is nearly impossible to engage enemy vehicles with vehicles. The infantry scouting and spotting is also almost useless because it is faster to go up to the hill with the vehicle and "look around". It is really arcade style and in my opinion it is unrealistic. As I know there is no radar which detect ground vehicles.
We made cover UI over the current radar to force players not use radar, but in some cases not properly cover the radar(different layout setup). With this radar cover the not only the detection functionality disabled but also the turret and vehicle orientation which is useful.
Check out the sample video, where you can see how enemy vehicle appear in the T-100's radar(Elite difficulty).
Suggestion 2 - Radar mode settings for each vehicle
More advance solution can be adding radar properties in the vehicle cfg and get/set functions for it.
vehicle setRadarType "NONE", "DETECT_GROUND", "DETECT_AIR", "DETECT_BOTH"
vehicle setRadarAngle 90-360
vehicle setRadarScan false/true (rotating)
vehicle setRadarRange 3000
vehicle setRadarSideRecog "FALSE" , "EMPTYONLY" , "TRUE".
vehicle setInvisibleForRadar true/false
And of course getRadar* equivalents.