* Start off small and scale big (either through expansions, product patches/enhancements, or training scenarios)
Which is the definition of feature creep. 
It's much better to plan for features from the beginning (when possible) to integrate them in the best way then trying to add them on top of an allready existing system.
Allow users to easily customize content they want to see and to the extent they would find helpful
Which makes a game almost impossible to balance...
I agree on your other solutions.
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"If i fight in the desert, how will the clothes and armor of my troops affect their morale and health? And how will the weather affect the result? How will the status of the war affect their morale? And the distance to our own territory? And what happens with my supply lines? If my opponent tries to attack one of my soldiers in difficult terrain, which is the chance of the enemy losing balance and...?"
Unnecessary micromanagement is a big no-no. No one should forget the uber mega maps that Frogboy likes to talk so much about. If i have to micromanage the breakfast of each of my soldiers just to make sure that he is at 100% of fighting capacity...
No no. Bad way to think about stuff.
There is no inheritent problem in adding complexity (or better said, detailed computation/simulation of certain aspects). It's all in the presentation and UI of things.
Let's say your units are in a desert. Now the game computes their efficacy in battle on the basis of the time of they day (how high is the sun?), amount of clouds, armor they use, how much water they've left, their race, etc. and as a result presents the player with a simple number (or bar, or any other graphical representation) that say, that unit is at 50% efficacy in this terrain.
It can be a very complex calculation (which in this example is probably a waste of computing resources which could be done faster with only looking at the terrain itself) but it's not a problem for the player in itself.
A complex simulation (or better, a very accurate simulation) of things doesn't make a game hard to for a beginner. A bad and unintuitive UI does and obscure game mechanics does. The best example for this is physics. I don't think many more than two or three dozen people on this forum are able to calculate more then some very simple classical mechanic equations, still nobody would protest that an accurate physics engine in a game adds too much complexity. Of course if physics would be presented to you in form of equations, you would have a point, but that's (hopefully) not what would happen.
Thus I declare your point moot. 
You shouldn't worry about complexity (besides it wasting developement ressource, about which I can agree with you) but about its presentation and incorporating it into a good UI.
(Yeah, I get really annoyed about people complaining about too much complexity, since I haven't seen a really complex game in the last two decades coming out. I've seen games with horrendous interfaces and very bad presentation which makes understanding them in an easy way impossible. But no games with reall complexity. Needing to micromanage things isn't complexity anyway, it's bad interface design. Or presenting the player with hundreds of in itself meaningless numbers isn't very complex either, it's again a case of stupid interface design.
I understand people being affraid of the need to have to micromanage too much things, since I don't like micromanaging neither, but that fear of "complexity" is imho misplaced, probably coming from bad experience with games with bad UI and even worse presentation, coupled with the need to micro things which could have been automated.)