There's a lot of features that unix systems have that Windows does entirely differently, or not that all.
To accommodate that, he'd need to either write high-level interfaces on top of things and/or use the subset of features supported across all platforms.
We already have Apache ;) I like NGinx because it's willing to say "Screw marketshare. I'm trying to make the best server for This use-case, and everyone else can bugger off."
You end up with platform-specific features, behavior and bugs, compounded across multiple pieces in the stack. You also end up with conflicting design decisions.
In my case, I wanted to use Apache & Python, but the recommendation is for a threading Apache on Windows, but forking on Linux (allowing e.g. mod_python).
To be cross-platform, I ended up going pure python webserver at the cost of performance and then had to deal with divergent cpython threading behavior, as well as postgres win32-specific issues.