Just a suggestion but I had an assignment that read "upgrade 3 tokyo town zones" which I decided to do. I did my first upgrade and and I didn't get any credit for it. then realized that I would have to FULLY upgrade 3 TT Zones. There is a big difference between FULLY upgrade 3 TT Zones and just Upgrade 3 TT Zones. needless to say I didn't have enough TT material to complete that assignment.
If the other mayors are truly getting different assignment options than me then the system is flawed as it's luck of the draw if you get enough higher values assignments to be at the top.