Currently, the distance for opponents for free-kicks, corner-kicks etc... is 0.5 meters. This distance is really small for adult-size robots and even for kid-size robots. I have trouble to see the motivation behind this choice.
In real soccer distance is 9.15 meters which is roughly 9% of the field length. To have something more realistic, I would suggest to have a distance of 0.75 meters in kid/teen (8.3% of field length) and 1.25 meters in adult (8.9% of field length).
The main issue would be the time allowed for repositioning when a free-kick is declared, it might be hard for defending team to reach a valid position in 15 seconds. Therefore, I propose to introduce the 'repositioning penalty' which would be similar to a removal penalty, except that the robot can move directly after the 'Execute' command is sent. Therefore, it would be a softer penalty for robots who did not make it in time.
EDIT: Was implemented for RoboCup 2019 without the repositioning penalty