Well, "generic battleship" begs the question of the manufacturer and the user. Battleships are ships constructed by very powerful factions that control entire planets and have gigantic industrial bases to draw from.
Sounds very samura industries to me.
The thing is, most corporation in Sirius could build battleship, and man them. The problem is, how could they deploy such things efficiently in a strategic way? beside, do they really need any with all the influence they have on the houses?
let's move on shipbuilding corporation though. They actually could begin selling battleships, but who would buy them? We have already removed corporation. Houses navy or police wont use them as they have their line.
That leaves the criminals and the neutrals.
We must remove every criminal and neutrals that have their own line of ships, or are known to use their allie's line of ships.
We might have junkers. While being someone who is opposed to junkers ever getting their line of capital warship, rich junkers could decide to have their own little mobile palace: a mobile smuggling vessel, less powerful than standard naval battleship, yet capable of defending itself.
But you'll see another reason, they will follow in my following explanations.
We might have Xenos. In their desperate cause, they probably have gained a few more people in the last few years with the social unstability, mostly coming from outside liberty. I can predict some strong sense of isolationism already spreading. Xenos are probably in this moment, gaining recognition in the liberty young, rebelious people. With secret supports, they might be able to aquire a few of these warships - probably through dealing with the junkers of course. They will of course be a very rare sight, Xenos being very restricted economically.
The unioners. Not only were they the workers of the Rheinland shipyards, they knew how to maintain a ship, because they built them, and maintained them til a customer such as the RM buy the ship.
Unioners should hence be able to live with a few battleships here and there as their mobile headquarters. I imagine they might have stolen a few older model when they formented rebellion. And through again the very long arms of the Junker, (which I always seen as an extremely powerful underground market), they might manage to possess a few more.
Cool, What about IMG and GMG, both are rich and powerful enough to not be ran over by a house. The GMG beat the tar out of Rhineland, all the Cap derelicts are testament to that, and the IMG is fighting a two front battle and surviveing with Outcast and Britonia. The IMG has to have something that says "MINE" and few things say this like a battleship. THough the IMG has very good ships in every other class that they have ships in. The GMG seems lacking and its hard to imagine they could hold off all Rhineland with just civilian fighters and mineing ships.
The GMG used raiding and hit-and-run tactics to defeat the Imperial Fleet. Not capital ships. So one could assume they used bombers to take down the battleships...
The IMG already have a few capital ships, but that's because "strange" and out-of-place ships usually go to the IMG. I don't think they need a battleship, they should have their own proper fighters instead of BSG ones.
both are again, mere corporations. While it is true they operate in more dangerous place, they can usually rely on bounty hunters among other things to safety their position. Let's not forget maintaining a battleship in operation should be a costly matter, an annoying matter, used mainly by militaristic factions - where junker makes a difference, is that they put themselves in some precary situation dealing with all these powerful pirates without in some way, showing them "hey, dealing with us is on neutral ground... otherwise taste some big guns." Plus, they are those that can pass down the big ship to the unlegitimate organisations. I can see them store a few non-operational on their guard system (apparently that base is a huge shipyard?), just waiting to be sold.
However, I dont know GMG line of ship. If they dont have a Battleship, this might be their ocasion. Logically, they are situated right next to the entrance of the outcast realm. They are openly at war against the largest drug smuggling organisation, equipped with large warships themselves. Let's not forget either, they are very near the corsair territories as well. GMG is in the worst place to be making business really. It also holds a near complete monopoly on H-Fuel, making him very rich. The time of the 80 years war are long passed, GMG has passed from rag taged miner into wealthy miner, but constantly in danger. In such situation of high danger, I can understand GMG get a civilian battleship.
Same of course can be applied to IMG, but I never felt they were as menaced as GMG.
I can accept this whole idea, as long as these battleships are less powerful than most others.