Allow turrets in the game for each of the races to have a specific anti corvette ability.
the three races would have a variant of a small AOE ability.
Advent-Tier 4 defense research
Loyalists: After researching tech level 4, turrets gain the ability to do a small short range AOE on corvettes doing about 25-50(+5 aoe damage per nearby turret, max +25) damage per hit to corvettes.
Rebels: 10% chance to revive (+2.5% chance per nearby turret) any destroyed corvettes (friendly or foe) within medium radius, passive effect.
Vasari-Tier 3 defense research
Loyalist: A turret ability that works like an AOE snare, short range, slowing corvette speed by 50% for ~30(or less) seconds for all corvettes it hits.
Rebels: Swarm of nanites that attack all corvettes near the structure at a short range doing 5 damage per second to all corvettes in the cloud
TEC- tier 3 defense research
Loyalist: A concussion missile that stuns in a small AoE doing 60 damage to all corvettes and stunning them for 5 seconds. longer cooldown then other racial/ faction abilities of this type.
Rebels: One flak cannon added to the turret to increase its anti corvette capability. Recommended use: clump em together.
This would allow people to cheaply defend their empire's structures against corvettes as long as they have the appropriate technology researched. High initial cost, short term corvettes would have the advantage, long term corvettes wouldn't be able to compete.