That's how it's been before, with other elemental games. The XML is included in its entirety in the save game. If you can decode the save game you may be able to make progress, but noone has so far.

Yes, but that doesn't mean you can test properly. Good testing relies on changing one variable at a time, and you can't do that if you're forced to restart the game after each change. You end up with some setup that works by accident, instead of working because it has to.

Here's a specific example. In LH 1.7 these are this vanilla AI priorities and tags for resource improvements:

Iron Mine: 5/Mining

Smelter: 100/Workshop

Foundry: 100/Crystal

Iron Works: 100/Merchant

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Crystal Quarry: 100/Mining

Crystal Mine: 50/Mining

Crystal Trove: 100/Mining

There's no possible way that this sequence makes sense. But it's also impossible to tell how to optimize it unless you can start with a single save point and play the same 25-50 turns with different values. Starting a new game doesn't work here, because a luckily-placed AI will never be constrained by the values you put here, and an unlucky AI will be affected too much.

You would have to edit the save files directly here as the save file holds all the data. But the save file needs to be decoded for you to make these edits and we have never had these tools.