Last year at the international competition, we tested out gameplay where robots that went fully into the goalie area were considered out of bounds. This removed the need for the double defense and pushing rules, and made gameplay go much more smoothly. Despite this rule being different from human soccer, it led to gameplay that looked much more like soccer - the current problem of the defending robot being large enough to cover a large portion of the goalie was reduced, and there was much less ref intervention. Both the referees and competitors seemed to like the change.
Proposal: Color the keeper box line white and make the keeper box out of bounds. All rules for out of bounds apply to this area. Remove the pushing and double defense rules (as they no longer apply).
I have seen some of these games and agree with you in the point, that the gameplay was better than in the regular games. Also the fields could be easily changed. But there are also points on the other side:
The field would get even smaller.
Last year nobody was prepared for a game like this. Because a robot is allowed to move in the penalty area partly, with some programming a goalie could defense the goal 5cm or 10cm forward nearly as it was before.
The size of the penalty area should be changed. In the current situation a robot does not really fit between the penalty area and the regular white line on the left or right.
I would say that this change would not do that much. The goal would basically be moved to the end of the goalie area, since no robot could enter it (like the real goal) and when the ball crosses that line the goal is almost certan. This would come at a cost of smaller playing field which is in my opinion not the thing that the new rules should contain.
The first question is: What happens if a robot touches the ball inside the opponent defense area?
The tactic would change. Now many robots nearly carry the ball in the goal as fast as possible. With this change the robots would try to control the ball and shoot it into the goal from where they are.