Yes...that is a very bad analogy.
Aaaanyways if you want some help I can Co-GM it for you but be warned I'm a bit flighty. So when I feel motivated I'll try to help as much as I can, but when I'm less so I might only to barely what is needed.
I also tried to do this exact thing a long time ago, but not enough people where interested and I lost motivation.
So for plot...Well to stick to the idea of Dragon Age: Origins. We could have it that our characters have as diverse a origin/backgrounds/walks of life and then they get recruited by Duncan. After all its not unconceivable that Duncan had some things to wrap up before Ostagar, he afterall in the Dwarven Origin was checking if it was in a blight in the deep road battle. And it makes sense that he would be makeing the rounds of Ferelden area to find new recruits. So for people that want to be Wardens they can do that, or they can come in later; like maybe they are apart of the army at Ostagar and the survive with the party? Anyways we could work around that and see what everyone wants for their character.
As for the companions in the game...well if people want we can keep some of them or get rid of them or they can make original characters to fill in their roles I guess. We can also play multiple characters if we want and add new characters as we want/need.
So list of possible Origins you can follow the orginials if their are ones or make it up whatever it just has to make sense.
Human Royal (Ferelden) Origin? Playing the Prince/Princess or Alistair type background.
Human Noble (Ferelden) Origin
Human Commoner (Ferelden) Origin? Originally planned in the game, but got cut.
Human Street Rat (Ferelden) Origin? Ya well lower end commoners underworld and stuff similar to the games Dwarf Commoner Storyline.
Human Savage (Chasind Wilder) Origin? Chasind are pretty badass marsh peoples check them out:
http://dragonage.wikia.com/wiki/Chasind_Wilders
Human Barbarian (Avvar) Origin? Part Native American, Part Celtic, Part Nordic, also pretty badass:
http://dragonage.wikia.com/wiki/Avvars
Human/Elven Circle Mage Origin
Apostate Mage Origin? Runaway Mage anyone?
Dalish Elf Origin
City Elf Origin
Dwarf Royal Origin? Re naming the Dwarven Noble Origin.
Dwarven Noble Origin? One where you are part of one of the noble families not the royal familes (that annoyed me).
Dwarven Commoner Origin? One where you are actually a commoner not a casteless/street rat like a merchant, warrior, minor cast.
Dwarven Casteless Origin? The Commoner origin under new name.
Surface Dwarf? Outcast from your peoples city?
Foreign Grey Warden? Maybe you where sent to be tutored in Ferelden, maybe you have just been stationed there, or have been there for years.
Etc. maybe your foreign? maybe you just don't fit in these origins, etc.
Basically we can count any background as an "Origin" no matter when they join the party.
Also some of the things the companions are we will need to have, or at least we should probably have if people take their places. Like we would need to have some connection to Flemith, maybe a different daughter? I'm not sure what she would do to her sons...
Also would be nice to have a balanced-ish party for combat roles, character roles (think character archetypes that fit in like smart guy, big guy, anti-hero, they might be more specific or multiple ones put together), and non-combat utility roles (basically anything not pointed out by the others mainly thinking along the line of who would do what on more mundane things like crafting or setting up camp/wilderness survival, charming silver tongued person who buys stuff for them, etc, etc.)