You have acquired your academic qualification as Mechanical Engineer and in normal cases you could have applied for different jobs in Govt or private sector or appear in some competitive exam but you are planning to do MBA or Masters in complex administration probably to enable you to acquire an prospective administrative job.
What I infer from your term 'complex' is that it is public administration.
If it so, then doing the public administration course will equip you with the knowledge of complex administrative issues in public as well as private sectors. It also covers the areas of policy making and it's impact in public matters.
The main subjects covered in such a course are - policy and governance, public safety and management, governing markets and environment and sustainability.
After completing such a course there are opportunities in Govt as well as private organisations where managers or project managers or assessment engineers are required for a variety of tasks.
The web of public administration is very big and encompasses all sorts of administrative issues which are encountered in business environment.
With those aspects and avenues in mind you can go ahead to acquire the said masters degree.
Knowledge is power.