I was wondering if anyone had decided to create a realism mod yet, or if anyone would be interested in this sort of mod.
Well, depends on realism. If you think about space combat realism rather
then atmospheric fight realism these are different things.
What is more important is that this is just a game and should be fun

So my comments follow... nothing important just thinking about
space combat.
(1) Make all ships much slower (though leave or increase the speed using phase lane jumping) Makes planning more important because you will not be able to quickly respond to an attack, you must have already prepared your defense fleet to counter any incoming forces. (IE A fleet in the Gulf of Mexico can't speed across the Atlantic ocean and defend Britian in a few minutes, it takes a long time to move a fleet)
In space, ships accelerate and decelerate but they can be as fast as
much they can sustain acceleration. Different thing is how fast they can acc/dec
Second in space combat terms beam weapons rule.
While earth fleet cannot fight at longer distance, fleet around Jupiter
could hit fleet around Earth with beam weapons in space.
(2) Make every ship in the game extremly fragile but more useful. Instead of having ships sustain insane amounts of damage from enemy ships make the damage more realistic. Once the ships are done or are penetrated the hull of the ship should begin to take extreme damage. One lucky shot can destroy an entire ship if you hit a vital spot! This should make combat much more tense as you try to get your ships in range of the enemy ships without exposing them to return fire. Each ship would die a lot faster, but at the same time be more important becasue they have the ability to inflict the same loses on the enemy.
Again, not very realistic for space combat.
Because of long ranges and low probability of hit, weapons would probably
have lower damage but could sustain constant fire. In that way fleets
could bombard each other for weeks till enough damage is done.
Ships would be probably very well shielded and armored in order
to survive space travel.
(3) Change the weapon systems on the ships so that they look more impressive. Instead of pooring weak fire onto an enemy vessel over the course of several minutes have one masive cannon shot destroy a frigate with a lucky shot. So a Kol Battleship will really be something to fear! It's heavy armor and weapons with long ranges will make it a daunting enemy to fight. Getting anything other than a battleship in range of a Kol would spell its doom. The same would go for the other factions battleships but each one would have its own special abilities. For example the Advent battleship would retain its heavy shields and have several fire arcs, allowing it to dive into enemy formations and take out several ships with sustaining heavy damage to the shields but none to the hull. This would create tactical situations where you need to decide if it is worth the risk to engage enemies when you don't have superior fire power or range.
Again this is realistic for fleet on the sea.
In space combat terms, firing arcs does not play that much of a role
because of ranges involved, so that several smaller ships could have better
chance against one bigger ( of course provided that they can penetrate defenses).
(4) Increase the role of strike craft and Long range frigates. - Fighters are no longer effective against anything other than enemy fighters and bombers. Would like to change fighters so that they use missles or beam weapons depending on the race to attack and defend against enemy bombers. Bombers slower but much more powerful. They will give your fleet the long range striking distance that is needed considering how fragile ships will become. Flak frigates and other defense vessels will become extremly important and would like to add a flak defense turret to the defense buildings you can place in your gravity well. Long range frigates will be like cruise missle launchers and will be very effective against enemy defense buildings but rather useless VS. enemy ships do the long distance involved and the high degree of missle jamming that could take place along with fleet movement.
Again fighters and missiles are not realistic for space combat.
Enemy fleet would have long time to destroy incoming fighters
and ordinary missiles with beam weapons.
Only realistic use I can see for fighters and missiles is
short range atmospheric/orbital fight for planet.
That means both attacking or defending planet.
Then again both fighters and missiles would have
hard time in dodging short range (probably tens of thousands of kilometers
is short range) beam weapons from space craft.
(6) Would like to make bombers or maybe an extra class of bombers that can attack planets as well. Would like to increase the number of strike craft you can choose from and increase the number of squadrons that can be carried on carriers. The carrier should be the most versitle ship in the fleet due to the wide range of things it can bring to the battle.
This is in my opinion ok as atmospheric bombers can play their usual role.
Just not to attack space craft, as their usefulness in space would be very low.
(7) Increase the range and damage of static defenses. Fighter hangers would obviously be more useful based on previous strike craft changes. The turrets would have an increased range and very heavy damage (Imagine how big a cannon could be if it never has to be moved once it is placed?) A shot from a static cannon defense should be able to destroy any frigate and two any cruiser. This will force players to bring in long range LRMS to deal with this defenses and give the defending fleet time to respond. Want flak turrets to defend from enemy strike craft.
Static beam weapon defenses should have long range , probably of novalith cannon

damage would not be that hi, though. Anything ballistic would be shot down before
even arrives.
Greets, hope this helps.