The ideal Aerospace Company to partner HAL to develop the MCA taking into technical, economic, political and reliability factors would automatically rule US companies out (the US government has the habit of issuing sanctions at the drop of the hat).
I would think of a few companies that can be useful:
- TsAGI (the designers of MiG-29 and Su-27)
- MiG
- Sukhoi
- Dassault Aviation
- BAE Systems
- MTU
- SNECMA
- Klimov
- Lyulka/NPO Saturn
- Rolls-Royce
These are largely, but not strictly, in my order of preference.