Hi Inderjeet
I had same thing in my mind like you and after discussions with experts/seniors/consultant & considering actual business environment, conclusion is here by priorities (as a business support consultant):
1. more & more involve in functional area & resolve the issues
2. go with MM (inventory & procurement part), closely attached to PM function practically.
( at present 60/30/10% queries are MM/PM/QM, we are receiving at PM end)
3. add QM, for equipment/material inspection process during procurement, calibration of equipments with Inspection lot/result recording etc.
Apart from this:
as a value addition or future scope- add PP and EHS, EHS would be more demanding according to current legal compliance's which are going more strict and compulsory for each industry.
enjoy 
parveenG