Yes, I think a "secret origins" thread could be acceptable. What's important is that the convulute backstory of a charater should not:
1) alter the past history of the planet
2) being needed to understand what's going on in the story thread.
As usual, to make the story easy to be jumped in by any new reader/writer.
Are you all agreeing over setting the story in the "real" world, where our characters, wheter superpowered or not, are the only thing different from reality?
That implicitly means that superpowers have to be caused by mutation or mystical orogins, no jet-pack for flying or laser gauntlets. Also, if a clone is created today, he will be just one year old next year, no instatly adult clones around, please!
If we all agreee over this, I guess anybody willing to is entitled to start the story. I have started the Vanguard Universe, this time I simply want to follow.