This is just something I came up with off the top of my head so don't rage, Perhaps the faster you go the harder it is to manuever i.e. turning, changing direction etc Small ships wouldn't be as affected by this but the fact that they slow down to turn could give the turrets on your capital ship some small chance to hit them, promoting the use of strafe runs by smaller ships.
On the other side of the equation we would have capital ships maintaining a lower average cruising speed to keep some manueverability, and so we wouldn't see big capital ships zipping around the galaxy at max speed.
As I said I came up with this off the top of my head so don't spam this particular area of the post with posts along the lines of, "I Don't want to lose what little manueverability I had in my titan," or " but manueverability was the only edge small ships had on big ships"- It is limiting the manueverability while moving not removing it completely, you would still be able to turn just not as fast as at a full stop.
On the other side of the equation we would have capital ships maintaining a lower average cruising speed to keep some manueverability, and so we wouldn't see big capital ships zipping around the galaxy at max speed.
As I said I came up with this off the top of my head so don't spam this particular area of the post with posts along the lines of, "I Don't want to lose what little manueverability I had in my titan," or " but manueverability was the only edge small ships had on big ships"- It is limiting the manueverability while moving not removing it completely, you would still be able to turn just not as fast as at a full stop.