With an eye on brevity and playability, i would suggest a limitation of the following classes for the core scope of ME D20.

1.  Animist - Not necessarily the D&D druid in the classic sense, but not necessarily a Ranger or a cleric eather.  This class should be able to focus on healing and natural environmental manipulation.  Core power should come from a divine source, likely one of the Valar, or all the Valar.  Note:  I would think only Noldor Elves or Dunedain taught by Noldor elves would really be able to properly observe Illuvitar.  I would suggest that all other races derive divine power from the Valar or their personal interpretation of one or more Valar.

2.  Ranger- Woodsman.  Limited/no magical abilities.  Much closer to the D&D 4th edition Ranger, and further from the 3.0 D&D ranger.

3.  Barbarian - Good ol low armor two handed weapon brute.

4.  Scout-  basing heavily on the scout class from ICE

5.  Rogue - Basing heavily on the rogue class from 3.0/4th ed D&D

6.  Marshall - Warlord, inspiring/tactical class derived from Warlord in 4th ed.

7.  Fighter- Trained warrior with all its variations.  I would tend to lean towards 4th ed fighters, as they have some limitations, but this ensures that an 'Axe fighter' is different from a 'Sword fighter'.  Rather than most 9th level fighters looking very similar in 3rd ed D&D.

Presige classes:

Priest - direct channeler of divine power.  must focus on and observe all rituals involving their chosen aspects of the Valar.  Probably begining to be accessible around lower middle levels.

Sorcerer/wizard - direct focuser and manipulation of their environment.  Power source comes from a combination of their force of Will/Charisma and thier inteligence.  Spells will need to be overseen and this should be a direcly taught class.  you cannot 'wake up as a wizard/sorcerer' you much build a relationship and be schooled by a wizard for a period of time to become able to experiment/learn on your own. 

Many of these suggestions are off the cuff ideas, but they all revolve around the huge single burning question.

Hawke, what things have a 'Tolkien feel' to you, and which do not?  Which part of the tolkien books feel 'especially Tolkien' and which parts of the books feel 'not so Tolkien?'.  Which parts of the Peter Jackson movies did you Love, only like, dislike and detest?