OK, why? You want a challenge, others don't. For a start, if the game is always a challenge, why level at all? What's the point of getting better if the enemies just get harder? As i said earlier, the whole idea is that once you reach a certain level you are effectively the most powerful person this world, and the game rightly reflects that. But out of interest, have you tried fighting the Greybeards? Most of them are level 100.
I think you and others are under the false pretense that "wanting a continual challenge" means that the game is AS difficult early on as it is when you get nearly the best gear and level up. The way it SHOULD work is that you "outgrow" certain enemies and grow into new ones. This should be a continual cycle that almost never ends. This is a TRUE SCALING system. In Skyrim, what this means is that you might have Bandit (1-10), Bandit Marauder (11-20), Bandit Enforcer (21-30), Bandit Highwayman (31-40) and so forth all the way up to the LEVEL CAP 81. This means that if you were level 30, Bandits are fairly trivial, Bandit Marauders are easy, Bandit Enforcers are an even match, and Bandit Enforcers are challenging.
This gives things a nice mix, now the issue becomes HOW to implement this. That is pretty easy, you would place the static enemies throughout the world in dungeons, ruins, and in the open world (tiers of zones). Any random encounter OR dungeon/ruin that is a part of a QUEST becomes scaled. Upon zoning in (similar to now) you would encounter a blend of tier of enemies. BASED ON THE DIFFICULTY SETTING would dictate what that blend was. For example, an adventurer that is level 30 who zones into a dungeon they have a quest for on Adept might encounter an even balance of Bandit Marauders, Bandit Enforcers, and Bandit Highwaymen - but NEVER a Bandit (1-10). A Novice player WOULD encounter Bandits, Bandit Marauders, and Bandit Enforcers but NEVER a Bandit Highwayman. A Master player might ONLY encounter Bandit Highwaymen. What this means is you are setting the LEVEL OFFSET of how enemies scale dynamically and STILL keeping static spawns in the world. This gives you the feel of progression still and lets you the PLAYER dictate the type of challenge you will encounter. TA-freaking-DA