That's great but as as the Jutes, an entire unit - Drekkar Dragonship Nordic Marauders is actually unrecruitable most of the time....why?

Because early on you unlock a technology that upgrades Nordic Marauders to Nordic Heavy Marauders. The tech for Drekkar Dragonships is much, much later than that on the tech tree - so when you do finally get there and build a level 3 Military port - the ship cant be recruited!!

You have to wait another 20 turns or so to get the next tech along and then upgrade the port AGAIN to get Drekkar Dragonship Nordic Heavy Marauders - which means 1 unit and 1 building tier is actually pointless.

Did Ca actually consider the unit upgrade system before implementing it, I may ask?