In short? Complete and utter bullshit. Take Eve Online, for instance. If you give people a varied enough world, people will always specialize and do whatever they feel like, instead of playing to some kind of 'meta' or 'must-have' archetype. Prime example? My main character is fully skilled and equipped to fly supercapital ships, some of the biggest and meanest bastards in the game. However, despite their power, they are a liability and need a LOT of support.
My point, though? I can fly some of the most deadly and dangerous ships in Eve Online, but I am rarely out of something larger than a Frigate, the smallest, fastest and 'weakest' armed ship class in the game. Why? It's my preferred playstyle, and with the right thought process in using them, every bit as deadly, if not moreso.
As a whole, Werewolf, I think what you're talking about here could do VERY well from taking a lot of cues from Eve and how open and fluid it is.
Eve has a lot of ups to it, but it has a lot of negatives aswell, I am still compiling what I call the World Rules. think about reality, we have our "laws" that we have tried to discern how gravity works, how time works, what do we need in our fundamentals to survive in our world, etc. call it, our understanding of the universe. Weather its by design or just the way things are, our world has certain rules that we follow, due to how we perceive it. I want to build a world with rules, with consequences for your actions, the fluidity of a variable creature system, would be vastly superior to an eco system then the static designs programmers use now, and is it that hard to design a system that uses one of the million of RNG systems in the MMO universe to spawn the eco system on a set of variables designed by the players by how active they are in an area?
Eve does a good job at giving people options to play in different ships, because its that kind of game, its designed to give people the option of playing a massive ship that can take planets out, but needs support or it would get overwhelmed, its a massive target.
To give you Insights into my mind about the situation for classes to be removed. I want to give people the chance to play a character how they want, and through that I have been working on a system I call the role system. as most of you know, the Trinity in MMOs, Healer tank DPS, is outdated and flawed. especially with how the current Meta of the games are working. new games are attempting to remove classes all together, but also remove the Trinity all together by letting everyone have the ability to do... basically everything. and I feel that its just gone out of control in the wrong direction. The Role System simplifies the character creation while diversifying each character to be unique unto their own. 5 Roles each with something unique to bring to the table. Tank, Healer, Support, Scout, Assault. Give Each Role "specialization trees", then think of the system being similar to Rift. Each Role is given base abilities, and each weapon choice gives certain attack choices upon a more ARPG system (click to attack styles similar to WotR/WotV or the ES series) then your specialization trees give you more advanced abilities, shift or change your base abilities to be more suited to what your "specialization" is. Add to all that, I would have people choose 2 of the roles for their character, and 3 specialization trees from within the two roles. Your two roles can never be changed on the character, consider that your "class". From there the specialization trees would be able to be so diversified, you could have someone healing with lighting, or bandages. you could have a tank, using his abilities with a 2h, or a shield, or minions, or magic. the possibilties would only be limited to the over arching rules of the game.