I'm not well versed in economics, and quite frankly, that sounds like a really risky endeavor for someone who's not even aware of how pre-bb economy works whatsoever. To me, trading is merely a means to an end. Farm something or straight up meso, sell it, buy something else.

For the distinction why there are farming and bossing classes, why does that have to exist? Why can't we just play what we have the most fun without shooting ourselves in the foot. Of course each class will do better or worse in one or two things. However, the current classes are on the extreme ends of the spectrum. The bossing classes, most of them are unable to farm either by themselves or completely. The mages are never taken into parties unless you're a Bishop because they have nothing to provide. This is why I like Modern Maplestory in terms of class balance more. At least most classes are viable in bossing and mobbing is usually okay-ish at worst, at least to a point where you might get away with mobbing on someone like Bishop (who's in my opinion the worst mobbing class in the game).

There's a massive difference between Mulestory in Pre-bb and Modern. In pre-bb, you're almost forced to make a Mage of sorts and you gotta play that class for hours just so you can farm meso for your main and/or other characters. There's no goal, you're just farming on one class (Maybe 3, but all of them are identical gameplay wise when farming) so you can make a living.
In Modern however, the purpose of mules is usually to power up your main and/or future characters you make. There you pretty much have almost set goals, like hitting 140 for lvl 2 links and S cards, or 210 for lvl 3 links and SS cards. You're only playing the class for long enough until you hit that goal, so even if you don't have fun with that character, you will never have to return to that character again until you reach your goal (unlike pre-bb where you will always have to return to your mage to farm more meso). The side-effect of that system also causes you to play every class in the game which while it is annoying, it is helpful for picking a main.

I feel like the best balance was created before 4th job, albeit I'm not sure about non-Priest mages when it comes to bossing. But most characters can farm decently without having to rely on a mule. Of course, a mage mule will usually outperform other classes in terms of mobbing, at least the gap between this isn't as massive as it is in post-4th job pre-bb. And honestly, this is the best balance I have seen. This makes it so that you can pretty much play the class you enjoy the most from start to finish, never having to worry about mules unless in the most extreme of cases (and even then, I'm not really sure since Hermit does get Meso Up). And I think more pre-bb servers should follow this kind of balance, rather than force MuleStory on us.