So far, I feel that ships can detect other ships too easily. From half way across the map, I am able to detect the enemy fleet and engage. Furthermore, all mission types currently follow the assumption that both sides have detected each other.
Sensors should take up ship slots, have a radius and range effect and either be on all the time, or toggled; generating flux. Stealth should work by reducing the effective scanning range of enemy ships, have an area denial - or blind spot that the enemy cant scan through or simply be a chance based electronic interference. Terrain should also play an important part in sensory interference, where nebula's should interfere slightly and asteroids and other solid mass should block sensors entirely.
Imagine this mission: you have a single scout with a narrow beam long range sensor, a passive electronics sensor (to detect the enemy ships sensor and relay their effective scan range and radius) and a number of sensor tags to mark enemy ships with so that they can be detected from afar: both in campaign and in skirmish mode.