Since I love Grimdark Future: Warfleets (and you should, too! Check it out now, it's free: https://www.onepagerules.com/games/grimdark-future-warfleets ) I've created several space ship designs that eventually led me to a ship generator - assembly and customize your ship as you already do with miniatures in my customizer.
Most space ships we know are rather elongated, have a front, back and several repeating mid elements, so I took this structure, too. You can just add as many mid elements as you like and then decorate them with cannons, armour and extra stuff.
You can find two already suitable libraries here:
https://cults3d.com/en/3d-model/game/dwarf-guilds-fleet-for-grimdark-future-warfleets
https://cults3d.com/en/3d-model/game/freighter-class-space-ships-for-grimdark-future-warfleets
To get full access to this (and all my other tools), become a patron now: https://www.patreon.com/c/Udos3DWorld