Pro's and Con's to adding DOI to theses ResearchGate offers to add a DOI on any file upload, if it doesn't already have one. I have in the past cited a few PhD-Theses that contain more information than potential papers, or were available before said papers made it out.

So I'm thinking assigning a DOI to a thesis that is published on the university repository can be helpful in making it more citeable.

Are there any downsides to this that I'm forgetting? Or further advantages?
From the ResearchGate website:

Advantages:


  
  Make your research citable. DOIs provide information on where your work can be found online. They are guaranteed to never change, making them a great way to provide a reliable link to any of your research.
  Showcase all of your research. DOIs provide the ability to find all publications associated with a single author, including research that hasn’t been published.
  Put a date on your discovery. DOIs include the publishing date of your research, to make sure you get the credit you deserve. 
  


Disadvantage:


  Once a ResearchGate DOI has been generated, the research cannot be edited. Instead, you should remove the research completely, re-upload it with the edits and then generate a new DOI.




Also see:
Should I include a DOI/website URL for a publication in dissertation bibliography?