Well I'd say leave it as it currently is. The wrappers here in druntime simplify the exposed interface to 'provides all/some (MSVCRT) C99 math functions, for each fp precision', so that a function is either not available or supported for each fp type and nothing inbetween.
Phobos' std.math already works around the missing MSVCRT functions, at least for Win64, primarily via assembly code. I'm not sure if linking x86 builds with MSVCRT is currently supported out-of-the-box, i.e., if each assembly code block for Win64 has an x86 assembly equivalent. These 2 architectures are obviously the main targets to be linked to MSVCRT, although ARM may become another one someday.
What I meant was that if someone's interested in implementing some of the missing MSVCRT functions, I think that should be done in Phobos so that it's implemented once for all platforms and thus making std.math more druntime-independent, rather than partially implementing libm here in druntime because of MSVCRT's shortcomings.