Start with an open system (but limited to notability) & let it evolve -- some "soft deletes" should probably go through AfD, just like some merge & redirects should, while others could be done immediately after the article appears.
I predict lots of edit wars as the people "deleting" the article will have no authority. Reposting deleted material without a good reason at the moment is clearly wrong, as it was deleted by an admin (who are considered trustworthy). If it can be deleted by anyone (including people who have no reason beyond AGF to be considered trustworthy), it will be like any other edit - ie. anyone can revert it (upto 3RR). With reposting at the moment, the default is to assume the admin was right, and that works quite well. With this idea, the default being to assume the random person that decided to soft delete it is right seems unfounded.
To summarise: If anyone can delete, we can't justifiably stop anyone from undeleting.
Counter argument: This is similar to the "PROD will never work because the article creator will always remove the PROD tag" argument, which has proven to be wrong, so perhaps this argument will also prove to be wrong and people will respect the soft deletions. I'm not sure the benefit over speedy deletions is significant, though...