Anyone ever see an anime series called "Legend of the Galactic Heroes"? It hasn't been released commercially here in the US, so fan subtitled Versions are the only real translations available. There might be enough ship types for both the Galactic Empire and the Free Planets Alliance to make a shipset, with maybe using one of the unique flagships to fill in the heavier ship types.
Though I wouldn't bother trying to match the fleets in the series. The 5000 ship maximum you can set in SE4 would make up a half-strength fleet in the Alliance Navy.
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"What do -you- want?" "I'd like to live -just- long enough to be there when they cut off your head and stick it on a pike as a warning to the next ten generations that some favors come with too high a price. I would look up into your lifeless eyes and wave like this..." *waggle* "...can you and your associates arrange that for me, Mr. Morden?"