MESMA is the least preferred option among existing AIPs in the world. Generally, countries are going for either Stirling Engine version or the fuel cell versions.
Not only MESMA is inefficient but it also requires a massive support infrastructure on base, which would be very costly to build.
In addition, getting two submarines off the shelf does not solve the problem. As of today, Indian Navy has 12 submarines out of which 7-8 are operational at a time. Navy is concerned about immediate future if Scorpenes are not delivered on time. It is worried about future in next 10 years time, not today.
So DCNS offer is fine, but no thanks. AIP will have to be different one and sub program would need further accretion in terms of additional submarines.
What Indian Navy badly needs now is SSN (nuclear attack submarines). Please somebody tell the political and bureaucratic leadership to give us nuclear boats. One SSN would be equal to 3-4 diesel electric subs.
If really DCNS is worried about Indian submarine situation, it would be lovely on its part to help us build "Barracuda" type boats. Will it do that???
DRDO fuel cell is based on PAFC in which methanol reformation takes place (using water) and H2 is produced.It uses phosphoric acid as electrolyte, that poses problem of corrosion, NMRL is developing special paint to avoid corrosion. It produces CO2 as byproduct.
Type 212 AIP is based on PEMFC which requires carrying hydrogen onboard and combines with oxygen to produce water as byproduct after releasing electron.
DRDO says its system is proven on land so it points that AIP will also be PAFC based in which H2 comprises 18.75% of weight of methanol. Also water is required for reformation.
Conformed DRDO AIP is PAFC based :
DRDO working on system to cut submarine vulnerability - The Hindu
This removes the need of carrying Oxygen and Hydrogen onboard. It may reduce the endurance underwater.
For information on DRDO fuel cell :
DRDO
For information on PAFC type fuel cell :
Phosphoric Acid Fuel Cells - scopeWe - a Virtual Engineer
DRDO presentation on Fuel Cell :
http://web.iitd.ac.in/~sbasu/seminar/presentation/3S.R.ChoudhuryNMRL,DRDO mbernath.pdf