I have expanded our map generation script to be able to draw the penalty box. You can find the script here: https://github.com/bit-bots/humanoid_league_misc/tree/penalty_area_rule_discussion
I was unfortunately unable to upload images to this forum so here is a link: https://imgur.com/a/HFhQMYV
I think the increased field border is good and might also help robots not to walk of the field so often.
The extra lines might also help localization algorithms relying on the lines. Since we want more Robots to use some form of localization, I think this is a good change.
Are there a lot of rule changes that would need to be made to incorporate the penalty box into the rules?
About the goal height for kid size: I would like to see a less high goal (with the same width) so the top bar of the goal can be seen more often and detected and used as additional information by teams.
The minimum goal post thickness is a must have. I agree with your proposed range at least for kid size. Does adult size need thicker posts since they must be visible from further away?