Bront said:
And I suppose that most people would rather be (the equivalent of) Ulysses in the game instead of meeting him in the game.
I think there is little doubt that warforged will be in the Monster Manual (them being in the MM is a way to support Eberron from the get-go), the question is whether they are in the SRD. That's one of the reasons why I advocated closing the MM races from player characters earlier. They'd probably originally be a gift/creation of Hephaistos, who might have collaborated with other gods. Perhaps created before returning to Olympus?
Eladrin are the 'fey wizards,' essentially taking on a role similar to high elves in 3.X. There has been a few hints that the eladrin types that exist in 3.X might also exist in 4E, though it isn't clear how. Elves are essentially wood elves, and more worldly than the eladrin. If the wizardry link holds, eladrin might be lesser spirits akin to, say, muses or moirae, though other connections are possible, depending on how they are depicted in 4E.
Linking tieflings to the titans points to a likelyhood that the titans are also potential patrons for warlocks. Seems fitting for now, but is entering rulesy territory.
The "too greek" problem I can certainly see. Some possibilities are to use a mix between greek deities and new deities (especially since there may be some need to cover D&Disms), and regional flavor (farther reaches of the main continent might have completely different cultures, and if there are other continents, they certainly should), worshipping the gods under other names, or other gods completely.