A wiki can support other students by providing notes and other resources for revision.
On a less altruistic note, a wiki can allow you to get experience in educational research by analysing usage statistics, as well as more generally in the educational sector - for example writing notes for the wiki is not, we imagine, entirely different from writing lecture notes if you wish to be a professor.
Finally, you may be able to obtain funding from Imperial via the StudentShapers program.
See the other wikis for examples of how a wiki is structured and functions. This will let you work out whether you can build one (with the assistance of a team). We will help with the actual setup of the wiki.