While digging around for information on extension loaders, I eventually found a reference to the following from the wglGetProcAddress() documentation:
Is this really a concern, or is it pretty much safe to build a set of function pointers once and just keep using them.Remarks
The OpenGL library supports multiple implementations of its functions. Extension functions supported in one rendering context are not necessarily available in a separate rendering context. Thus, for a given rendering context in an application, use the function addresses returned by the wglGetProcAddress function only.
The spelling and the case of the extension function pointed to by lpszProc must be identical to that of a function supported and implemented by OpenGL. Because extension functions are not exported by OpenGL, you must use wglGetProcAddress to get the addresses of vendor-specific extension functions.
The extension function addresses are unique for each pixel format. All rendering contexts of a given pixel format share the same extension function addresses.
It looks to me from the above that there is no truly kosher way of using the WGL_ARB_pixel_format functions.