So, everyone who's played Empire will know that a vineyard, winery and a marble mine are vital to prevent getting stuck without marble early in the game, which for the Empire ends the game.
I was rather disappointed to play a game against an Empire AI, to find out that it got stuck. It did build a vineyard, winery and a marble mine (one vineyard, one winery for three marble mines). Unfortunately, it had built its roads around the vineyard so tightly that the vineyard's productivity was zero. So no grapes, no wine, no marble (on a completely flat map I made myself - may upload it later once I find out how that works). And that was the end of the AI. There was plenty of space, and no limitation whatsoever, so just some bad decisions...
So, a friendly suggestion from my side: if the AI does a check whether productivity of the vineyard is 0%, perhaps it could reroute roads as a quick-fix, or even remove the nearest building altogether (together with the road leading up to it)? As a more general fix, the AI should build more vineyards anyway. It appears to think that 1 is sufficient... and so even when it gets its marble economy going, fails to expand it.
I did a few double-checks, and whether the AI is aggressive or defensive, it appears to often place the vineyard very close to the headquarters, which often gets very busy with roads. It happens very frequently that the vineyard doesn't work. On maps with some height differences (e.g. using the " height noise" in the editor), this problem seems not to occur, since buildings are less dense.
p.s. I play "build 18". p.s.(2), map uploaded: https://wl.widelands.org/maps/flatlands/