woops .. wrong assumption. :o Cleanup indeed doesn't do this. Suggested to check out the tool cause after I skimmed through the manual once, it looked liked it would do something like this to me. I'm an impatient reader, u see. :nervous:
Like Michael mentioned, the Quadrangulate and Triangulate work quite well.
They can help you to split a Ngon into multiple triangles and make a quadrangle from 2 adjacent triangles. So to cleanup Ngons, using these tools, u would triangulate first then quadrangulate.