Thank you for your elaborate answer, Tuidjy.
I don't question your experience and knowledge in programming a tactical combat AI and therefore don't disbelieve in your judgment. Even more, I can not argue at the same level of knowledge, as my own experience is (mostly) that of an user of computer games, not that of a programmer.
All in all, I think, it boils down to the question: "How clever do I want the AI to use the given rule set?"
Personally, I am willing to live with a far from perfect use! I am new to this forum, but if you would know me from the civfanatics (Civilization 5, for those few, who might not know the forum), you would know that I don't have that high expectations of what a computer program is able to achieve in tactical combat at all! I am pretty aware of the limitations given by a complex rule set and I am fine with the idea of AI bonuses (e.g. in numbers) to compensate the human supremacy. 
But I believe, that the tolerance to AS (artificial stupidity) is a personal attitude and I can perfectly understand the wish for equal preconditions for both: AI and human player!
So, let's label my suggestions as "Would be great to have, but they are illusionary." OK, I could live with that. Keeping them in mind as a nice, but unachievable utopia, we could limit our wishes to what is possible and necessary. And here, we come to the main reason for my first post:
When I saw an archer shooting through a forest in a "Let's Play" video, I was shocked! Sorry, but in all willingness for an AI streamlined programming, this is a simple No Go! It was such an immersion breaker that, if this stays in the final game like that, my shortly inflamed love for FE might burn down to ashes instantly. As I said in my initial post: tactical combat is such an important part of the game! Having an at least a halfway decent system, is crucial for the game. At least in my eyes.
Even more, there are games already on the market that can pass at least this task with flying colors - and they are old: Remember "UFO - Enemy unknown" and "Jagged Alliance"? Boy, where these games fun to play! (And there are/will be new incarnations of the game, as we all know.) Both games lived, because of their fun tactical combat. And their battle maps where larger and more complex than that of FE. But I don't even ask for such a decent battle system. Just:
Let's forget about the proposed movement restrictions, if AI can not handle them in a decent way. Let's forget fighting mali (I think they are called "negative bonuses" in English?) on certain tiles, if this is too complicated for the AI to use. But please, PLEASE overwork the archery algorithm! Don't let shoot archers through forests (and other impenetrable objects)! It is not even necessary to teach the AI to make good use of the cover. Just let it use it "by accident". I would be fine with this.
(And, maybe in addition, introduce my proposed range limitations for archers. I think, even *I* could program an algorithm that teaches an archery unit to approach the enemy until a certain efficiency threshold (lets say 75% of their maximal accuracy) is reached. This would make TC more interesting, without rising impassable barriers for the AI.)
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Sorry for being so annoyingly stubborn in this point. But, after all, this is the FE Wishlist thread, isn't it? And this is my MAYOR whish!