The first to think of this? Naw, not by a long shot
In any case, my homebrew is based Heavily off of Tolkiens works, mixed in with Earth at about 1050 CE with the assumption thrown in that every myth, folklore, legend and religious concept is true. So, the world is in a Dark Age with hobbits in their shires, elves in their woods, dwarves in their mountains, humans on their manors, and monsters pretty much everywhere else
In any case: magic system:
Elements of Magic: Mythic Earth Revised is
the magic system you should be using for this. It has it's new base classes. Basically the idea is that each spell has 2 round casting times (except for signature spells [special spells developed by/studied by you], which have 1 round casting times) and you can craft whatever sort of spell you want. It's completely open-ended, and is brilliant, to say the very least about it. Also less powerful than the core system, but more versatile (which is something you'd want with Tolkien, IMO).
Other than that, you're going to want a few different classes for D&D in Middle Earth:
Barbarian - there are really very few barbarians in ME. Considered having this as a PrC.
Bard - again, few bards- though possibly common among the elves and to a lesser degree humans and maybe a few rare hobbits.
Cleric & Druid- covered by the EoM Mage class.
Fighter - there are many warriors in ME, so this stays.
Paladin and Monk get ditched.
Ranger - fits right in in ME.
Rogue - fits right in too.
Sorc and Wizard - covered by the EoM Mage class.
Other classes which I think would fit in:
Archivist (HoH) - could work.
Beguiler (PHBII) & Dread Necromancer (HoH) - make great foes, like Sarumon (Beguiler) and Sauron (Dread Necromancer). Yeah, I know, over-simplification, but you get the idea
Knight (PHBII) - fits in with the fighter types.
Marshal (MHB) - fits in with the fighter types (especially if you give 1:1 BAB, like it
should have).
Noble (DLCS) - plenty of nobility in ME, so this works.
Scout (ComAdven) - Scout fits in nicely - better than any other splatbook alt class.
Thug (UA) - could fit.
Anyways, just a brief 2 coppers on my behalf.
cheers,
--N