Overloading in Smallwiki

Hello, I am a trainee working on a small project with Smallwiki. I am mainly interested in all the security issues. Formally, my project was about the IP filtering. This approach seems to be not really relevant because of the dynamic IP distribution by internet providers. Just by logging out and logging in a new IP can be obtained, and could potentially upload again, whereas an innocent user can be banned because her/his ISP just could have given a banned IP. So, let's take an another approach. Do you think it would be useful to only grant the upload of some Mimes-types and only allocate a clear space disk to users and groups of users like 50MB/day/user or 100MB/user, or define a clear file size allowed to avoid the flood. I could maybe do it if you think it is useful. Let me know. Thanks Cheers Eric Luisi