I find the complexity of the game high enough and don't see any reason why it should be increased (I think it should be a pretty good one to do so). And I read about more and more ideas, which are only getting the game more and more complicated... If all of them were implemented, I think the game would become more or less random clicking game, because no one would be able to understand it
Overall, I quite like complex things, but only if they are not too complicated in its base; if there are more and more unnessesary rules added, the fun and playability disappears...
What's the point? Should the player spend several months just learning the basic rules and then years by trying to understand them and learning how to use them in his favor? My personal, quite recent experience of an absolute beginner: First two month of my playing I had constantly opened warpedia in order to learn very basic attributes of units and to figure out why something did not go the way I supposed it should (repeatedly forgetting some bonuses and similar things). Now, after five months, I still have to open it quite often, though only for minor issues like which unit is better for plundering. Not mentioning a lot of very important rules (namely the 90% rule in battles) is nowhere to find, except for that they are mentioned in some old threads in forum.
There are cca 350 players at all now - I would like to see more players to learn the game and become competitive in reasonable time.
FOW is increasing a complexity in way you have to learn how to use your scouting units properly and you don't see your opponent's progress (but if you want to play melee games and are curious about that, you can get quite enough info about it from the stats).
But the change like this completely changes the game mechanics. First, you have to learn and remember how each season affects the map/units. That is, you have, say, twice as much information to learn. When you are done with this - even more difficult (at least for most people, I think) and time consuming task begins - you have to learn how to use all these information together in your favor.
Now I have some small target I would like to achieve (for example getting some important city). I choose some units and plan their ways depending on the terrain, some income sites and ruins nearby and so. Sounds easy, but I find it also very easy to lose some turns on it or arrive to the target too weak because you made it in a wrong they. I can't imagine that I should take into consideration that map would change several times during the process or I should count whether my group arrives to that city in the exactly bad time. This sounds for me like a task for some super genius or walking encyclopedia...