I am not sure if radar works on EnigmaUO, however since you guys are using 5x UO client then it probably does. In very early UO there was a spell Bird's eye which was basically a mini map, which was later converted into a radar system. IMO it would be much more fun and 'Ultima-like' to add this spell, instead of using a radar. (if it's possible).

UO Demo, for instance, has Bird's eye script somewhere in the core files...

If i remember right your talking a bout Wis Uus which was a first circle spell. Im all up for this however i believe the client controls the radar and we wouldn't have any control of who uses it and when.

But perhaps it is possible to edit the radar so that without a spell effect it will would be dark on the radar...

Perhaps, we'll see what what can be done.