It's just a feeling i get reading the various faction posts.
There's lots of PCs trying out for there own faction, and i feel as a result most factions go nowhere for lack of people.
I've had many people ask me to join a faction, and i've made PCs to join such and such project, but most have aborted real quickly.
So based on that feeling, i'd encourage folks:
A/ to stick to their idea, because you'll get nothing done with a one week old PC
B/ to join existing factions instead of trying to make a similar one (ex: militias or similar)
That was just my 2c.
Sometimes there are IC reasons to try and make a faction that is pretty much the same as an existing faction, without wanting to join the one already in place.
if you build it, they will come
My advice:
Have a somewhat generic plan for your character. And a fairly flexible background. Then let your char develop organically, as opportunities and options unfold themselves.
Make friends, or at the very least, allies. This will bring you into far more plots than trying to force your way in.
Once things start rolling, you may find that you don't have near enough game-time to keep up.
That's just my 2 cents, if a tad off-topic.