I agree this should be something to consider in the future. I know it existed in one form or another previously and gave Stardock some trouble. Check the mods. I play without mods most of the time so I won't be much help here. 

I'd say if they added multiplayer (not that I want this) there would be a case for the ability to remove roads. 

This sounds like a problem that is meant to be solved by using outposts.

Outposts force enemies to go through an area at regular speed even if there are roads present, and the roads still help the outpost owner.

Caltrops make outposts even more effective at this function.

If you place the caltrops strategically around your important cities, their zone s of control will just conquer them again right away if they get captured.

If you can't get around from one area to another quickly enough there is always Cloud Walk and Call of the Titans that can get you around the map to defend your stuff.

I think the developers gave us these tools so we could overcome the advantages that roads give opponents.

I always thought it was pretty weird that capitals of two nations on opposite end of Island will magically have roads to each other capital as soon as they agree to economic treaty even when it paths through like 100 Fire elemental nests.

Even more weirder is that some caravans actually manage to survive and reach the capital at end of road.

I don't see any good reason a pioneer shouldn't be able to build roads.

I wouldn't mind having an easier time taking road building as a trait for trained units either.

I am fine with the roads being made instantly and all that other stuff.

Besides, since you can build roads "on the fly" which basically can quadruple the movement points of the building unit (of anyone who has the trait build road), its proably good its restricted

Would Raise/ Lower Land work for removing roads? I've not actually tried it.

Raise/Lower Land preserves roads (since you can't actually create impassible terrain with it.)

EDIT: gotta watch those ninja parrots

If you want to really mess with the opponents, take both Master Scouts and Earth Magic and judiciously use Raise Land to make everything into hills.  

Put it all over your own and neutral territory on every tile of non-enemy ground.

It will reduce their movement considerably while not affecting your own.

You can limit their movement to a crawl with outposts (your territory), raise land, and caltrops.

Even if they do manage to conquer the outposts, they will still be stuck with raised land.  The land won't prevent you from re-conquering the outposts.

This strategy is pretty mana intensive, so you will probably not want to have a Mage sovereign if you do this.

I would never be that cruel.

Seriously, though, I wish it were possible to make it so the game would never generate any swamp tiles.

Even if you pick mountainous you will still get swamp tiles.

If you pick swamp that means you have a large possibility of getting screwed by swamps yourself and that is just horrible.  Better to just pay the mana to craft your own terrain based defenses.

This isn't an answer for the original poster, but you can make a really cheap army that only builds roads.  Give them a wooden club and the road building perk.

They're pretty efficient for 3 dudes with wooden clubs.

In the Stormworld (for base FE) mod, Greenskin and Lizardmen factions/races had no movement penalty in swamp. The Greenskin faction is not in CoS, and the Lizardmen race no longer has the ability.

I have so far played without mods, so swamps still prevent me from building things.

I snake all my cities, so it prevents me from putting crystals and whatever else inside the walls.