vandalism fighting is more of an issue when anonymous users edit or add pages. the site administrator can define who gets edit permissions on an xowiki instance basis. oacs has means to ban users. xowiki has variuos means to locate recent modifications and keeps a history of the changes that one can switch back to earlier versions.
I am not saying that we don't need better mechanism for such purposes, but we are in a different situation than the oridinary wiki. Currently i am more thinking about making the package more powerful.
btw., the good thing of an open source project is that everyone can contribute...