MagisterCultuum
Great Sage
It has never seemed right to me that all roads in an empire are equal. Improving technology should allow better roads to be built, not just speed up movement on existing ones. What if early on you can only build paths, which can be upgraded to trails and then to real roads later. It doesn't take a specialized worker to beat out a rudementary path, so either most units should be able to build them, or perhaps they build themselves if enough units move through a tile. Weeled and maybe mounted units could require at least a path in order to ender a tile. Late in the game you could built a King's Highway-basically like a railroad in Vanilla, maybe with slight defence and/or healing bonuses, but which cannot coexist with other improvements or terrain features like forests. Perhaps there could also be toll roads, which require other civs to pay the roads' owner for the privalege of passing. Last but not least, religion specific roads: RoK civs with Arete can build tunnels or mountain passes which allow their units (only with RoK promotion?) to move through impassible terrain. FoL civs can build hidden paths (you can guess what tech this needs), which grant their units invisibility and commando while on the road (letting FoL units move freely in rival teritory), but can only exist in Forests, Ancient Forests, or Jungles. Perhaps only civs with FoL can see that these exist. To make these useful, you may need to let workers build these from 1 tile away (like some spells work). Because of the obvious qualities of hidden paths, these changes might be perfect for Shadow.