I think you are quite correct viz inter force cooperation. Which is a shame but true.
MHA in general has been a steady buyer of Indian (i.e. OFB) maal, which is a good approach as you should save your best for the 3 services.
What is the use case for SPH in BSF? They will not be maneuvering into enemy lands backed by arty fire assault.
They can begin with 130 mm Catapult system to begin with. Or at least 106 mm RCL and BMP based mortars: