As my comments suggest, I didn't quite succeed... so I'm uploading what I've got so far for two purposes: so others can have a crack at generating what was requested if they're up for it, and also because I think what I've created could be interesting and enjoyable as it is.
This map is simply an open central area surrounded by forest, with each players' starting area nested within the trees. There are four themes, each of which are the same layout, but with a different visual style. The resources are just standard for any map.
The requested effect was that each player would have to travel through the centre of the map to get to any other player, and so creating a battlefield. This is not quite achieved here as the lines of trees to either side of each player do not extend far enough into the centre of the map. This effect may be somewhat achieved by playing 3v3 or 4v4 games, as players will have to cross the map more to reach the enemy, or by playing on a smaller map size than the usual, so the central area is smaller and all the players are brought closer together.
Anyway, if anyone wants to take this and try to fiddle with it to get closer to the requested map, feel free, and if you should succeed, let me know how you did it!