I may of course be entirely wrong...
You are entirely wrong.
They cannot form a significant part of the Navy without being major warships.
They'll build the navy they need and not the one that looks cool. They won't build capital ships - and capital ships carry spinals - when they know there isn't even a remotely plausible threat from other capital ships.
Another fact you're continually overlooking is that we're discussing ~ -1000 and not 1105. The Confederation doesn't exist, it's Darrian and a handful of tiny scattered colonies.
We're looking at
one world here. Darrian does all the heavy lifting, pays all the bills, builds everything, and educates everyone. Darrian is it and her colony worlds are dependents instead of economic assets. Remember, it took the biggest colony, Mire, nearly
800 years to build starship after the Maghiz.
They lacked a direct, immediate external threat...
That's true. They also lacked remote, long term external threats as actual history proved.
... but they knew other starfaring cultures existed...
That's true also. They knew other starfaring culture existed and they knew where those culture were located -
several sectors away.
... not all that far away.
That's a deliberate misconception. It's been repeatedly explained to you what the Istvin Fleet knew and when they knew it.
They also had to police their own worlds...
One world and scattered handful of tiny outposts. Nothing that would require spinal-armed capital ships.
... and interstellar interests.
What interstellar interests? They don't have any interstellar neighbors closer than a sector away and they neighbors they do know about are multiple sectors away. What "interests" do they have that require force projection in the form of spinal-armed capital ships.
That is why I suggested cruiser, or cruiser-like, ships rather than battleships.
You suggested cruisers because they're cool, because having your Darrian PCs flying around in TL 16 unbeatable cruisers is just as cool as having your
D&D PCs flying around on tamed red dragons.
This isn't
D&D though.
Traveller has to make sense.
If the TL 16 warships were not armed with spinals or many factor A+ bays no-one would care about them.
As already explained, their electronics and sensors would still make them useful and would still allow the Swordies to win wars. That last part is another fact you're continually overlooking; the Darrians lose wars. Even a single partially operable ship like the one you're suggesting would make thos know Swordie victories extremely unlikely.
If the Darrians have the "red dragons" you want them to have, how do they still lose wars?
The still-working TL16 warships may of course be only propaganda.
TNE's RSB
Or the Darrians might have something like a Navy Depot that can still repair and even build a few new TL 16 ships...
They don't.
... solving the mystery of ships still working after 2000 years.
TNE's RSB
I think we have to agree to disagree.
We can agree that you're wrong.
Canon is not very detailed...
It's detailed enough to know that you're wrong.
See though, that the Itzin is told (CT:AM8, page 8) to be formed by 35 transports and 10 armed escorts. So over 20% of their fleet was armed whips, and, having to cross the whole former Imperial space (that was becoming a chaos), those armed escorts are likely to be on the cruiser size range. They were no alien to warship needs.
I agree with. I'll also point out that the Istvin exodus takes place
300 years before Darrian starts building starships, that the Istvin exodus required different type of warships than any new Darrian navy would, and that those Istvin ships were funded/built by a far larger economic system in far larger number of far larger shipyards.
Assuming the former paragraph is true, the armed ships the Itzin took with them are likely to ha espinals and large bays...
I don't see spinals in the hands of trading companies, even as the RoM unravels.
I also don't see the Darrians slavishly copying the design rationales behind the warships in the Istvin Fleet when their immediate warship needs are so much more different.
Finally, I'll ask you the same question I asked "Dilbert" and the same question I've been raising since this topic began:
How do the Darrians lose wars?
If they have TL 16 spinal-armed capital ships, how do they ever lose naval battles against a TL11 or 12 opponent?