Right, so I've reread your RP and this is what I've gleaned. Please correct me if I'm wrong.
First, I believe you claim to be an amalgam of two ID's, Freelancer and Junker. From what I gather you want the ZOI of the Freelancer ID so you can sell scrap in Kusari without getting blasted by Kusari factions, but you also want the Junker's scrap/p-scrap mining bonus that they get (or something very close). In order to 'compensate' for these positives, you have willingly allowed yourself to have a cargo restriction 700 units less than the Junker ID's, and you withhold your claim to the Pirate Train.
So, basically, it's a Freelancer ID with the scrap/pscrap bonus and use of the Junker shipline, including their Salvager.
Do I have the sense of things here?
If so, let me say that you are taking the best of two ID's with little downside for yourselves. This is the whole reason we have the one ID per faction rule. It prevents factions from sidestepping the restrictions imposed by the ID they use. The Junkers do not have the diplomatic freedom to fly through Kusari space, but you eliminate that by using the Freelancer ID. The Freelancer ID doesn't have a scrap/pscrap mining bonus, or the Junker shipline, but you eliminate that by using your Junker alts. Now, if I'm right, you want a Tinker ID which gives you everything in a nice neat little package. The sacrifices of making the move to 3600 cargo is insufficient. You don't need a Pirate train, because as your RP (that I did read btw) suggests you are not pirates, so that's no loss. It would be a wonderful OP setup for you.
Basically, you've almost achieved a neutral ID with a premium mining bonus. You don't engage in unlawful activities, so no lawful faction will come down on you. You're rep would be neutral or better with most unlawful factions in Liberty, save Xenos. Kusari lawfuls would leave you alone, and Kusari Corps would allow you dock on their bases. You'd undoubtedly be flying Salvagers, since you view yourselves as Junkers, but would expect all the other factions to view you as Freelancers, giving you the optimum ZOI. It's hard to find something to dislike in this setup.
As far as server balance is concerned, we have enough Junker official factions. There is not enough opposition to the Junker ID right now. Xenos get ganked by everything that moves, and Hogosha hardly exist. Even if the other Official Junker factions accepted you with open arms, the server itself doesn't need another Official Junker faction, especially an OP 'hybrid' one.