Navigation locked out during operations? I don't seem to be able to navigate around while trying to do some operations. E.g. when using the E command, I can't mousewheel to zoom. Is there some way of changing that? It's incredibly annoying.

I've been through the key mapping and there doesn't seem to be anything clashing that needs mousewheel as far as I can tell.
I don't think you can, select what you want to extrude then dezoom as needed before hitting E .