You could simply increase the scan range and decide depending on their size how to go on. Or you write your own c_scan function:

you = ent_next(NULL);
while(you) {
if(vec_dist(your.x,...) < 500+your.max_x) {
just do it
}
you = ent_next(you);
}

If you need a scan cone in your own scan function, calculate the angle from the scan position to the entity and compare it to the scan direction.