How can I help with support for the MSVC compiler on Windows?

You would have to maintain a patch set separate from KiCad. The lead developers have unanimously agreed on February 12th and 13th of 2013, that we will never support any version of MSVC++, or any future compiler coming from the maker of that compiler.

We will not accept any patches with the intent of supporting this compiler, ever. Any posting about this topic will be considered as spam, even questions about the policy.

Given this policy statement, no expectation of even a response to such an email is justified.

The compiler we do support, and will support on Windows is MingW. It is settled.