this is in the next beta 0.6.5, membergroups can be set to be able to "submit" articles/news and they will be set to "off" and "unapproved" initially. Then admin can "approve" them in the submissions page, and place them in the right category etc.
In addition membergroups can be set to "pre-approved". Their submissions will show instantly and they can choose category. Still no editing rights for those, but i am working on it, and plan to have that in 0.7beta.