It think the idea of a pending status, where more experienced people choose and submit to the final category, is a good move. That way the work that someone does with a submission isn't wasted and they get some help from the system.
I still think that it would be a shame to reject submissions just because they don't fit a strick sub-category or that a category doesn't exist. In that case it could make sense to put them in the general category where they best fit.