I do get what your stance is - you want a fast travel system that doesn't let you go everywhere in the game willy nilly once you've discovered it. However, using a Morrowind style system is very close to what you're suggesting - only being able to travel between towns. What I was suggesting by turning it on / off however is that people who just want to jump in, do quests, get rewards and money, finish the game should be able to do that, and people like yourself who have time / desire to have a longer, more enriching experience should get to do the same. Perhaps by making a hardcoe mode like I mentioned earlier, fast travel could only be restricted to towns.
With the method I'd design fast travel, you could travel to every location you've found - just like in Oblivion. Only that I'd remove the easy button factor of it.
Essentially you'd have these choices:
To get from Anvil to Imperial City, you could choose from these:
Manually travel there, with your feet or your mount at no cost, unless you run into trouble that you cannot run away from.
Get a boat that gets you there for 200 gold. You wont get into any trouble on the way.
Fast Travel there recklessly for no gold, but you'll likely run into trouble on the way. You might arrive there at night when the city gates are closed and you need to wait until morning, climb the city walls or levitate over them. The bandits you ran into also chipped away 1/4th of your health and some durability from your gear.
Fast travel there cautiously for 50 gold. You'll end up at your destination in good condition. The trip will take longer in-game time, because you tried to avoid fights (although not completely). You also had to sleep in Inn on your way there.
The interface would also allow you to skip using an Inn, skip using methods of transportation etc for less cost but more chance to run into danger - almost just like in Daggerfall. You could also travel to locations you didn't know that were there, mostly cities and towns if you pay for your trip, then you don't have to be the guide or know the way.