The Holy Roman Empire.
Peasants as strike craft.
Landsknechte as frigates.
Clerics and captains as destroyer-carriers.
Knights as cruisers.
Nobles as capital ships.
Generally low-tech, lots of ballistics and some missiles but no beam weapons. Lots of armor, little if any shields. High firepower and long-range, but inaccurate and very forward-focused.
Fighters and frigates both would generally be equipped with low-ROF, long-range ballistics and have the ability to grapple close-range enemies, slowing them down and dealing modest damage over time. Of strike craft, frigates and cruisers, there would only ever be maybe two types each, with little loadout flexibility. Consider these massed, expendable units only good in large numbers.
The fighters would have plain, functional looks. The Frigates would be garishly colorful, with more than a little flourish in terms of shape.
Fighters and frigates would need point-defence and a proximity bonus to performance by the destroyers, which would in turn have only frigate-level firepower on their own (for the captains, not the clerics). Destroyers would be largely a support category, serving as small-scale carriers and force multipliers. Their special ability would be instantly reloading all nearby frigates' and fighters' weapons.
Cleric-type destroyers would either be dressed in sacral colors (catholic) or plain black (lutheran). Captain-type destroyers would show off their thick armor plates, with only a little banner here and there.
Cruisers would generally fall in two categories: Knights and men-at-arms. The knights would have a large number of subtypes, each with different specializations and various quirks (alpha-strike missiles only (Huntsman), no normal propulsion but a high-acceleration movement ability (Robber-Baron), side-mounted shields and a close-range weapon that deals damage in proportion to relative velocity (Jouster)...and so on). The knights are to keep the enemy on their toes. They would have various shapes, but usually a heraldic color scheme and pattern.
The men-at-arms would come in a single class with no special abilities, but would be the only class to have significant loadout flexibility. These would be there to let the player handle threats the other, less flexible ship classes can not. They would be aesthetically plain.
The capital ships would be fairly balanced, not nearly as overspecialised as the smaller vessels. They'd generally have some of the traits of the smaller classes, but to a much lesser degree: The Archbishop-class fleet support vehicle would provide proximity bonuses and point defence. The Prince-Elector-class Heavy Battlecruiser would have some of the unique weapons of the cruisers in addition to its all-round armaments. Both Archbishop and Prince-Elector would have the special ability to take a fugger loan, i.e. repair their systems and reload their weapons, but repeated use could lead to engine failure or magazine cook-offs. The Holy-Roman-Emperor-Class Battleship would be a spanish Tercio in space - strong armaments for all ranges and situations, four times larger and more resilient than the next-smaller craft, and with a special ability that gives it a boost in speed and deals damage to all rammed vehicles (including friendlies). However, the HRE-Class BS would also occasionally get excommunicated and shut down for a random amount of time. There could only ever be one such BS in existence at a time, as is proper, and you could only get it in exchange for a Prince-Elector-Class BC, in addition to a huge stack of gold.
If possible, the whole faction would occasionally break apart and fight silly civil wars, but eventually be united again.
Had some plans for it, but other projects took priority.