The suggestion: Make it impossible to gain 100 Symp with very easy missions. Who is going to trust someone with the really interesting things who just ran 100 simple delivery jobs?
might be like:

very easy: max 20 Symp
easy: max 40 Symp
normal: max 60 Symp
hard: max 80 Symp
very hard: max 100 Symp

Which WOULD cut some ways to get 100 symp that are used now (for example handing in enough very easy recycle missions that can easily be bought and handed in), but would get more use out of other missions, and increase the pressure to rework the mission system (make more missions interesting). The easy and normal recycle missions for example are surely not used mostly, for example.
It might be best to only set that in WHEN the missions are revamped somewhere along the road though.