The only possible weapon I can think of that could cause a kill at 15,000km without saturating an area of space are guided missiles, which the IN isn't big on. There's no need for them - just drop them.
According to revised fluff from FFG, IN cruisers can be fitted with guided missiles, which are slightly longer range then macrocannons. It is not, however, common. At least in the Calixis Sector.
Er, no it doesn't. It makes no sense whatsoever. Even the weapons you describe would not be able to fire at those ranges. Also their ability to predict the location of manoeuvring bombers from so far away so far in advance is ludicrous. That's not even taking into account the cover the ship itself would provide. Oh, and the fact that this is all being accomplished by secondary weaponry with no loss of primary weapon power. Ludicrous concept.
Sigoroth, this is space. Projectiles don't lose power until they hit something. Just about every projectile weapon is range = infinite. As everyone likes to say about orks, fill a volume of space with munitions and you'll hit something.
"Gunnery Chief: This, recruits, is a 20-kilo ferris slug, feel the weight. Every five seconds, the main gun of an everest class dreadnought accelerates one to 1.3% of light-speed. It impacts with the force of a 38-kiloton bomb. That is three times the yield of the city-buster dropped on Hiroshima back on Earth. That means- Sir Issac Newton is the deadliest son-of-a-bitch in space. Now! Serviceman Burnside! What is Newton's first law?
Serviceman Burnside: Sir! An object in motion stays in motion, sir!
Gunnery Chief: No credit for partial answers, maggot!
Serviceman Burnside: Sir! Unless acted on by an outside force, sir!
Gunnery Chief: Damn straight! I dare to assume you ignorant jackasses know that space is empty. Once you fire this hunk of metal, it keeps going til it hits something. That can be a ship. Or the planet behind that ship. It might go off into deep space and hit somebody else in ten thousand years. If you pull the trigger on this, you are ruining someones day, somewhere and sometime. That is why you check your targets. That is why you wait for the computer to give you a damn firing solution. That is why, Serviceman Chung, we do not "eyeball it". This is a weapon of mass destruction. You are not a cowboy shooting from the hip!
Serviceman Chung: Sir, yes sir! " - Mass Effect 2
As far as the ship providing cover, I remind you that, at least in this game, most of the time ships don't even provide over from other ships firing their main weapons at a target on the other side. Cover is (mostly)a a non-entity in this game unless you're a planet or something similarly large
Not when the Despoilers are still fresh in everyone's minds. IN would still be very, very wary about a new almost, purely LB ship because of what happened with the Despoilers.
Why would the Despoiler be fresh in anyone's mind? According to the fluff for the Gaerox Incident, the Inquisition covered the entire thing up afterwards, so only the members of high command at Bakka and the Inquisition would know what went on. (which is why the more or less lack of AC is considered an aberration by IN standards) What little fluff we have to go on for other sectors occasionally mentions pure carriers in the employ of IN.
I think I'll swap Jovian for dominion in my list. People seem to like that much better.
Of course they like it. It's an Armageddon with 4 lbs for +15 points. That's a hell of a weapon upgrade.
Then to think Sig and I developed MMS. Talk about changing. 
Or where we started about a 90* Protector years ago.
I did not ask for a restriction. I asked for a removal. Insert the Dominion from the Book of Nemesis. 
I'll admit, I had to ask an eldar player what MMS was, since no one I know uses it. If what he said about it was true, I feel for you. His reaction was right up there with Sigoroth's views on SM lances.
Dominion is ridiculously powerful. If it was brought into this list, and not restricted to 1 per fleet, the list would probably immediately replace Armageddon as the most common competitive IN list. Combine it with Gothics and a Vicky and we'll see a new dawn for the Torp Beamer build.
And aside: Mercury is better, now, but still could use that torp swap.