Haven’t played any of the franchise
Have I misunderstood kingdoms - is the experience diminished by not exporting the battles to the battle games or have I got it all wrong?
To answer your questions in order:
1.) Yes, you have.
2.) No, it is not.
3.) Yes, you have.
The combat system in Field of Glory: Empires is actually pretty dang decent. It stands on its own, and I'm quite certain it will in Kingdoms as well.
If you want a quick overview, just watch the first few minutes of this tutorial video (narrated by Dastactic) that shows off the game's auto-combat:
It's easy and straightforward, yet also still provides reasonable results given the troops and terrain involved. And of course, you can still simply auto-resolve entirely, or export the battle to Field of Glory II if you wish.
Honestly, the ability to export battles to Field of Glory II is a neat feature, but it's also something a gimmick -- one that is entirely unnecessary to the enjoyment of Field of Glory: Empires. I 100% guarantee it will be just as unnecessary for Field of Glory: Kingdoms as well.
Quite frankly, I think Slitherine over-hyped the ability to export battles to Field of Glory II, and I'm concerned they're going to make the same mistake with Kingdoms. I'm pretty sure that by doing so, they caused -- directly and/or directly -- sales of FoG:Empires to suffer, as a lot of folks felt it would've been necessary to also purchase FoG2 in order to have the "full" experience, and thus they didn't purchase either game (unless they already owned FoG2).