Why MPC and Noir are a good fit:
 
1. Noir is lowered to ACIR, an intermediate representation that consists of 7 opcodes (making the evaluation of it rather simple) and is backend agnostic. ACIR can be used as an entry point, greatly reducing complexity as one can reuse the Noir compiler.

2. The ecosystem is designed to add support for proving systems, i.e., we can just write a co-SNARKs backend. So, we do not need to hack around the ecosystem - we can just leverage everything because it is designed to do so (we had to fork circom to build our co-SNARKs as the intended use case was not to add other proof systems).
 
3. The witness extension is the most complex part to support for co-SNARKs. For Noir, we can support a large portion of all possible circuits by MPC-ifying the most basic opcodes of ACIR (simple solver of equations which is fine in MPC).