I suggest the Ark because Illustrious at present has a use as a replacement for Ocean, and the recent Illustrious refit allegedly removed much of her ability to support fixed wing aircraft
I suggest regenerating Sea Harries because the Indians already fly those (though an earlier version) so there would be more commonality than using Harriers
As for Somalia - I tend to agree, but the fact is the UN is going to try and get food in there somehow and will hit problems with the local terror groups. But even if you ignore that, having a flat deck off the Horn of Africa would be a good deterrent to the pirates. We've got the carrier sitting doing nothing, India has the manpower, we both have the aircraft. Put it all together into a jointly manned project to maintain skills