I'm not sure if this is the right place to point it, but being new to this mod gives me much to think about it, and something just did not go right in my mind about fixed borders.
The whole concept is great, to be able to control tiles in war or just in the wilderness makes things much different. But this not only means controlled territory, it means a lot more.
In domination victory it may lend a hand in winning if you only lack territory to get the victory. Not sure if this can be exploited hardly.
The other point seems more problematic and already happened in my games. When you make a tile of your control far away from home, you suddenly have that tile fully covered by your economy (which can be centered anywhere on the map relatively to the spot you just snatched), which means you may upgrade your units (if they don't need a building, or if your tile has any connection with your commercial network to provide the resources needed, or if it doesn't need neither of them). This is strange, but acceptable. It's hard because only units that don't need resources to upgrade may do so, or well placed plots may lead you to desired upgrades.
The other and more problematic issue is the maintenance cost. As suddenly as you grab a tile for you, in the middle of the enemy, on another continent that you have no presence but an army, your stack of 100 units suddenly cost you nothing for being far away. This is an awesome way of making infinite wars (if you can manage the war weariness and your enemy's attacks as well).
This is not only ilogical, but it's also game breaking. I don't understand much about programming stuff, but in my mind Fixed Borders should only allow you to grab tiles adjacent to other tiles you own. With this the one tile surrounded by enemies wouldn't exist, and even seeming you would lost the capability of snatching far away resources with fixed borders and a big road, you would still be able to do it, but now you need to make a far away city (not exactly a good substitute) or a fort (indeed the good substitute). Forts could keep like they are because they are exactly the answer for trying to grab far away land without risk of rebellion or a great maintenance cost.
But far away single tiles with full economic support are bizarre.