The Battlefleet Gothic mod is now compatible with Entrenchment 1.041 as of 1/17/10, and has a new version (1.30) out as of 1/17/10
This mod contains the Imperial navy in a fully modelled state, and Chaos, the Tau and the Orks in a proxied state.
BE WARNED: THIS MOD IS STILL RATHER BETA AND IS MISSING MANY FEATURES, INCLUDING:
-A research tree (unlocks, colonization, fleet supply, cap ship crews and long range jumps are quite literally all that's there (well, there's a missile tech, but it doesn't do much, and you WILL be able to get late game ships early)
-GUI elements. some 2D icons aren't done yet, and the ones we have are a bit odd. They will be fixed eventually.
Things that we know about (IE we know about it and it's odd, but it's either a design decision which will be explained or something not implemented):
-Counter description text. It's wildly off and somewhat arbitrary, but the ship descriptions are pretty good and should give the player a decent idea of what to expect, and I'll write more on them on our forum (link here).
-Shield Mitigation. It's gone, but it says it's at 15%. Trust me, it's gone.
-The Emperor Battleship. As a compromise on its heavy dorsal armament that can be fired to either broadside, we made it have the strength of the dorsals and a broadside point forward, and slightly stronger broadsides. We think it works pretty well, but please tell us what you think.
-Chaos ships and tau ships in the Additional Races Compendium are odd. The chaos prow weapons are locked to fire left, so they can broadside well to one side without turning into brawlers and tau weapons are locked forwards so they can concentrate fire, but they lost their ability to fire at half strenth to the sides because multi-arc weapons are impossible in sins as far as I know.
-No stock sins races. GW wouldn't let us include them, and they have a very different gameplay mechanic anyway, and need a very different setup for damage types, much to my chagrin, seeing as I want to know how it'd end up 
.
Okay, now that that's out of the way, we can get to the fun stuff. The ships are working great. If you know the tabletop game you'll know the key things that I need to tell everybody else so they understand the game.
-Ships turn and fire SLOWLY. You need to think ahead, and you can fit in a lot of micro if you know what you're doing. This is intentional.
-Shields recharge VERY VERY VERY VERY FAST. This is a legacy of it being a tabletop game where focusing fire is a big achievement. Shields will fully recharge in the time it takes for you to fire a second salvo of your weapons. Firepower supremacy is big here, and so is using your weapons to their utmost. However, hulls repair rather slowly, so protect them.
-Ships will go up like popcorn, even caps if your fleets get big enough. A fully experienced cap has quite a bit of damage absorbing ability, but it isn't even close to invincible. They're about twice as valuable as a cruiser, and if you're careful, can absorb 3 times as much damage easily. It's a great bargain, but they will die, don't get attached to them.
-Oh right, cruisers. There are cruisers in this game, and frigates are now fragile scouts and flankers. Frigates are cheap, expendable, and surprisingly dangerous in numbers. Cruisers are a lot bigger, much tougher, and carry a good bit more firepower, but a really big price tag. Battleships come in on top, and are really durable, and host a lot of long ranged firepower.
-The weapons are different too. Weapons batteries and Lances are your basic weapons. Lances are focused beams of energy that do best against escorts (accuracy) and armored ships (penetration power, but with just the imperials that isn't that big an issue). Weapons batteries are massed guns that do best against battleships because they can actually be expected to hit a lot. They aren't that different, and the range and strength of the guns means more than their type. Torpedoes are great. They punch through shields 100% of the time, but tend to drop off against bigger targets, which boast the point defense turrets to shoot most of them down. They make great escort killers, and are your best weapon in smaller fights.
-Attack Craft (fighters and bombers) are also very different, they come in squadrons abstracted to one ship, and are much more fragile. They're also much more dangerous. They, like torpedoes pierce shields and can do a lot of damage, especially against smaller ships (including cruisers, battleships are nasty to them though). However, every ship has turrets that can kill them, but if they stagger their waves, they can hit home very hard. They also replenish quite fast until their parent ship runs out of antimatter, so they're really quite good. Fighters are quite capable at interception duties, if you have more fighters than the enemy, your bombers will be able to strike enemy ships while your ships are safe from enemies.
Please note!
-Planet capturing is quite different from in standard sins. The transport is your one stop shop for planetary warfare and colonization. They land troops instead of bombarding. The whole idea is a little bitcomplicated, and I encourage anybody who's interested to read the thread I'll post on our forum shortly. The short version is that you build transports, use their bombardment ability to pound your enemies into dust, and then return them to the munitorum depots (they have the advent antimatter recharger icon for now, shouldn't be hard to find on the screen) to refill. It should especially suit the Imperium's style of defend and counterattack.
Now that you know the basics of the game, you can download the mod here:
DOWNLOAD (7ZIP, 109 MB) (This should work properly but I've been having lots of problems with it, if not, please tell me so I can remove the link while I fix it. )
7zip or winrar both can open 7zip files, and both are available for free, and much smaller than 50 MB.
DOWNLOAD (ZIP, 162.63 MB)
And please visit our forum at Modcraft if you want to learn more about the mod and what to expect, volunteer or give detailed feedback:
OUR FORUM
Dev Journals: These guides will help you know what to expect in the future and understand the current state of the gameplay.
Dev Journal 1: Ships of the Imperium It explains all the imperial ships and their fleet's way of fighting. Should be useful.
Dev Journal 2: Fleet tactics of the Imperium It focuses on the use of the Imperial ships in a fleet. Definitely good food for thought, may apply more to tabletop than the mod, I need to test the theories some before I fully endorse them.
Gratuitous screenies:
Gothic class cruisers pummeling a Dictator class cruiser with lances and torpedoes
Retribution class battleship firing its prow lances and torpedoes at an enemy cruiser.
Finally, the trailer for the Imperium (thanks again, Thrawn!)