Such a comment coming from a think tank equivalent status is disappointing.
Karachi is already divided into six districts for management issues. There are 114 police stations in all 6 districts.
The other different branches are:
FIA,
Special Branch,
Operations branch,
Investigations branch,
Anti extremist cell,
Sindh Reserve Police
and Counter Terrorism Department.
The SSU is a different branch.
Traffic police department is also separate.
ANF or Anti Narcotics force is also a separate department.
To complement Sindh Police, the whole contingent of Sindh Rangers is deployed along with police. Infact Sindh police is hardly seen alone in any operations, Rangers are always with them.
There is a branch of CMI (ISI) dedicated in combating crimes in Karachi especially towards car lifting, car theft, car snatching etc because such vehicles are then used in anti-state activities, which makes it difficult to track afterwards.
I know of the NATO container tracking project completed by NLC in 2007 in Sindh, Balochistan and KPK from Karachi ports to the borders of Chaman and Torkham all along the highways.
Mate, all the measures are in place.
If the establishment accepts your reason of "hundreds of paths entering into the city" and cannot monitor and manage different routes entering Karachi with the all the strength and departments mentioned above, then the establishment has failed and the security management of Karachi should be privatised.
