[Savannah Knights] 1st level spellcasters in d20 Modern?

I want to play a modern fantasy game. Okay, to be more precise, I'm helping Acquana (Jessica Jones, DM of the Savannah Knights Storyhour) fully flesh out rules for her campaign, and I intend to use the system too.

For those of you unfamiliar with the setting, there's a link to the storyhour in my .sig.

Here's a refresher on how the world works:

• Originally, magic existed on Earth, but during the dark ages, a war waged between the humans and the magic-using races. The humans were victorious, and part of the conditions of victory were that the magi were to retreat. There had always been a Fey Realm, tied closely to our own world, but at the end of the war, the fey realm and the human realm were separated, and almost all magic-users were forced to leave our world.
  
  Today, the two worlds are known as Terra (the human realm) and Gaia (the fey realm). There are still connections between the two worlds, though travel between the two is much harder now than it once was. In more modern times, agreements have been reached to allow some creatures from Gaia to live on Terra, but the existence of magic remains a secret to the general human populace.
• The people of Gaia include pretty much anything that exists in human mythology, and they are collectively known as magi, usually. You also have the true fey, the Unseen. All magi are able to use magic with little difficulty, if they choose to learn it. Similarly, humans with some magic blood in their heritage can use magic naturally.
• Humans have two routes to magic. First, they can study it as a science, using bizarre rituals and strange incantations to cast spells. Most such arcane lore has been forgotten, but old texts still exist, and a few orders still practice magic this way. Second, many humans are able to bond with the ghost of another human, and the ghost acts as a conduit to magical powers. A human with a ghost can learn magic with about the same ease as the magi.
• The setting is not just modern. We want it to be able to handle anything in the setting, which could include events in the Dark Ages or the Old West, or could take place entirely on Gaia, without ever dealing with Terra.
• We want to use D20 Modern as the primary ruleset.
• We'd prefer to have only one magic-using class. We're not sure if it should be an advanced class (The Magus), or if we should create a 7th ability score of Magic, so we could have a Magic Hero to go along with the Strong, Fast, Tough, Smart, Dedicated, and Charismatic heroes.
• If we go the advanced class route, we still need a way for characters to use magic at first level. We're considering having various magical talents available for Smart, Dedicated, and Charismatic heroes.
• There are two types of ghosts that you could get magic from. There are the above-mentioned conduit ghosts. In this case, the ghost is just sort of like a familiar, and has little power of its own. The second type of ghost uses its own magic, and can cast spells and such even if it's not bonded with a human.

We need rules that can handle all of these things. We'd prefer to make the system d20 Modern compatible, rather than making a new, slightly different game. What suggestions do you have?