WINE has been reimplementing the Win32 ABI (not API) for decades. It already works pretty well; development has been driven by both volunteers and commercial developers (CodeWeavers) for a long time.

There are many programs that still do not work properly in WINE, even though it has been developed for decades. This in itself demonstrates the infeasibility of reimplementing Win32 as a stable interface on par with Windows. The result after all this effort is still patchy and incomplete.