Clearing mines
Entrenchment needs mine-sweepers!
AS has been noted by several other posters, I strongly recommend that a mine-sweeper frigate or cruiser be incorporated into the game. When the AI (or perhaps other human opponents for those who play online) engage in mine-spamming it can significantly impair mobility in a star system if done extensively enough. While the idea of being able to place mines is great, every move should have a counter-move. I'm currently reduced to using a "spare" capital ship as an "ice breaker" when I feel I need to clear out a field.