Wish: When a field is captured, destroy all objects, and reset the downtime of already destroyed objects to maximum. As an exception, ack is rebuilt on capture as it is today.
Why?
Human nature likes easy targets. This frequently causes two countries to fight the third. There's no bad intentions involved, its the simple fact that attacking a less defended target is easier. Once that mode is reached, it doesn't end easily. It requires a significant shift in numbers, long distances to the next field, no further fields to capture, or similar. Alternatively, massive porking efforts by the country being attacked.
Full destruction on capture adds an inconvenience to a continued push in a single direction. It suggests switching targets more frequently, and by that helps to reduce the duration of 2-on-1 situations.