I'm not sure about how extreme a change you're looking for. Would you eliminate all of the time and work required to access a battle (camping/pop killing for NMs, seal farming and travel for BCNMs) so that you just teleport instantly to a spawn point and click an object to start? And once you're finished, you're guaranteed the drop?
Alright, we might just be having a small misunderstanding here. No, that would be far from the case. Think of something not all that different from a conventional RPG, where you would travel through the dungeon, facing battles and/or puzzles along the way, and finally face the boss. Maybe there would be some battles that took little travel or effort, and they were just that hard. I'm talking about bosses where the solution is not "level moar"... where you actually have a true test of skill to endure, and you might be looking at a half hour or hour long fight. Those kinds of battles could potentially require little "warmup" effort.
But the thing of course is that the battles are actually challenging. Rather than killing an NM 5 times because you didn't get the drop the first 4 tries, you're likely to fight the NM 5 times because he -killed you- the first 4 tries.
You mention randomness as a solution to the nonstop farming of high-end items that would result. What does that mean? Unless you're talking about something cheap like varying the level of the enemies between easy and impossible, there isn't anything you could randomize that would daunt a competent, flexible player. ****, even if only the top 1% of players on the server could handle it, that would be enough to flood the market. It doesn't have to be just braindead people following an online guide.
What I'm talking about is strategic randomness. Let me give you an example. There was an optional boss in FF9-- I can't recall its name, but it was the hardest boss in the game. Even if you knew the best strategy for beating him, there was still a very good chance he would kill you, just depending on when he used what abilities. And FF9 is a very simple game, strategically speaking.
Of course some items can and should be "EX". Tons of the best equipment in FFXI can't be traded, and yet there's still an economy. Though personally, and speaking as someone who readily benefited from the ingame economy, I don't think having a strong economy is that essential to the game. If anything I'd probably prefer the economy to be reserved for smaller trades, not for the stuff that's very rare and valuable. But we can forget about that discussion for the purposes of this one.
My point was that 1% can't flood the market if they can't trade the reward. The result would just be that an elite 1% of players would have it.
I promise, I'm not a *********. I think a 5% drop rate from a monster that's difficult to claim in the first place is out of hand, which is why I never bothered with them. And relic weapons are so extreme that they're downright unhealthy. But a 25% drop rate on something moderately camped? **** yeah, bring that on. And I recognize that other people's tolerances for that stuff may be higher or lower.
What it comes down to for me is being rewarded "fairly" for doing what one is supposed to do in these kinds of games. I mean, the primary drive for all these games is to kill ****, and make your character better, right? Most people want to do just that... they don't want getting to fight to be by far the most challenging part of the fight. Camping NMs is kind of like hunting deer or pondfishing irl-- incredibly boring to most people.
Now excitement-- that's walking into a bear cave empty handed and planning on coming out the other end alive. People enjoy doing that kind of thing in a video game knowing that if they die, they get an extra life. It's not about the cosmetics. There's no challenge in walking through a cave of stuffed bears. And likewise, fighting a mob that looks tough but really isn't doesn't excite most people.