Personally, I think the system's fudged up enough that it'll never be as consistent as we'd like. FJ's system has a somewhat similar issue, in that the destroyers have 500 series registries but the scouts also have these, as well as 600 series registries. The ships are ordered chronologically by number, and while this happens with the cruisers as well, it makes some sense there.
I myself like the idea that you can have a series number for a specific class, ideally without much overlapping but it might occasionally occur. The series number has little to do with the order of the construction in relation to other classes, but serves mainly to identify that class. In some cases you might have numbers carrying over between refits and upgrades, as Ships of the Star Fleet does with its frigates.
I myself like the idea that you can have a series number for a specific class, ideally without much overlapping but it might occasionally occur. The series number has little to do with the order of the construction in relation to other classes, but serves mainly to identify that class. In some cases you might have numbers carrying over between refits and upgrades, as Ships of the Star Fleet does with its frigates.