I think I'd be in favour of the "everyone's a little Force sensitive, it's up to them what they do with it", maybe make it that it takes a lot of time and quests to become a proper Jedi.
Someone who wants to start as a Jedi would have to spend a few days as a "youngling", restricted to whatever academy they start in and lacking in money and skills when they leave to join the game (e.g. You leave the academy as a level 5 Jedi with nothing but the robes on you back, the level 5 smuggler you meet on your first planet already has a few hundred credits and a custom pistol).
Oh, and I dunno if we're still talking about MMOs with a single player mode, but... Phantasy Star Universe. In the offline you played a set character and followed a story, in the online you created a character, formed parties, quested, hunted for rares, etc.