Oblivion's Fast Travel easily eliminates the challenge of braving a trip back to safety after you've been especially battered, and removes the importance of coming prepared, considering how using it has no consequence.
get that nobody wants to constantly backtrack through familiar areas;
But that's no excuse to strip away the game's challenge like OB's FT has done.
Enemies and the world itself should always be a concern.
Ah, but here's the thing - with the way the respawn system worked in the previous Beth games (areas only respawn after 3 days have passed without a cell being loaded into memory), the guy who walks back and forth between town and a dungeon? Doesn't face any new hostility, or danger, or suffer any additional loss of items. Because "backtracking through familiar areas" has no danger, as there are no new enemies.
Which is exactly why I like FT in Oblivion and Fallout 3 - I like to explore, and not having to tramp back and forth on foot through huge swathes of NOTHING, allows me to use more of my limited time to tramp on foot to NEW places. Full of places I haven't seen and actual danger.
And the best way to keep the challenge while removing the tedium of normal travel is through a system akin to Fallout 1 and 2, with random encounters,
Yes, that would be a good addition.
Another one I thought of is plotting out your fast travel on the map between points you know. So, if you've been to a dungeon north of Anvil, and you've been to a dungeon north of Skingrad, but you haven't explored the places in between those two dungeons? Your FT path has to go through places you HAVE been... (south to Anvil, east along the road, north from Skingrad). This would make more time pass. Also, you could combine it with the "random encounter" concept, and have more chance of an encounter if your plotted path cuts straight across the wilderness. (Of course, the game could be programmed to pick this kind of path to start with - every location has a "closest town", and all FT routes are "return to closest town, travel between towns on roads, head out to other location". Unless both locations you're traveling between both have the same "closest town". Or something like that.)