There's been a ton of servers like this. Check out this video:
https://www.youtube.com/watch?v=eeLQ2GDQhY8
Blood of the Akkadian, Edge, Enlightened Dark: Ascension, Sanctuary, etc. All have/had a ton of custom content. Some have been more successful than others.
The problem with most servers, imo, is the amount of boxing required to progress. No one has any idea how to balance a server around 'classic' mechanics.