It doesn't matter whether or not you represent a student union, society or campus service. Bringing the Dead Thesis Society to your university can make a difference in helping your fellow thesis-writers feel connected and productive. First, think about the kind of thesis support group you want to have.
Some universities have thesis support groups coordinated by an office of psychological services.
It has been our experience that anything that looks like 'group therapy' will scare away more people than it helps. You may find some useful information in our backgrounder for university administrators . Try to get funding so your meetings can be catered. Every campus will vary in the amount of involvement and support you may get from each of these players. At the very least, they should be aware of what you are planning.