Workshops allow pupils to upload work and for peer and self assessment using pre defined mark schemes, puipils can also be marked ontheir assessments. However there are time limits that need to be set and I find that apart from large assessment they are to much work for me to manage. A Workshop with manual control and the option to save and reuse marking criteria would be needed to make me use them more often.
I am looking into Using forums, There is the option foreach pupil to have their own discussion, the other pupils could then write constructive feedback and add grades, It would not be easy for you to collect all of the grades in though.
The other way is for pupils to just rate the submissions to the forum (use zip folders for assignments that need more than one file uploaded)
You could post an assessment guide with the assignment instructions.
Hope this helps.
Rick.