This is not a computer game. There will be no code. The gameplay will be discussion, talked out between the players and referee. This will play more like a tabletop rpg than a computer game.

"Talking out" such an hardcore simulation (a game about computers simulating fleet designs) like a roleplaying game is not possible. In a wargame, common sense and sportsmanlike niceness allow players to fill in gaps in the rules, in the interest of having fun with a challenging game. But here, who can say titanium hulls are better or worse than steel hulls? Who decides what weapons are possible, and how effective they are? The game would devolve into pressuring other players into deciding that my designs are good and your designs are weak or cannot be allowed, with no rules to speak of. In a roleplaying game, the shared purpose of narrating a story or following along with the GM's ideas and the shared framework of fictional and aesthetic references (e.g. lasers are OK, planet-shattering beams are not OK) mitigate this kind of toxic interaction.

A good simulation needs strict rules: a catalogue of available parts and complete strategic and/or tactical rules about how they work against each other in combat.

I would make players build fleets incrementally, "buying" a predetermined amount of parts per turn after spying (partially) what the other players are doing, and then run a battle after building is complete (one battle, for game length reasons, and therefore a free for all clash with symmetrical starting conditions).