[ToddF]

The number of crossings required to take down a defense, and the number of goals required to capture the tower are semi-fixed by the number of lights on the ramps and the tower. Changing the requirements would either be confusing or require hardware changes to the field.

There are, however, some simple rule changes which might make breaches and captures more difficult.
breaching:
1) All five defenses required to breach.

captures:
2) Increase the number of boulders allowed in a tower from 6 to 8 or 10.
3) Reduce the number of boulders on the floor from 6 to 4 or 3.
4) Offensive robots prohibited from entering the secret passage regardless if a defender is present.

both:
5) No penalty for defenders interfering with defense crossings. (eliminates shooting from defenses as a safe zone)