Thats what my suggestion is. Update w32api (already being done) such that both ReactOS and WINE can be compiled with it (and the platform SDK headers too) and move anything that doesnt go into w32api from the ReactOS and WINE existing "API" headers out and into wherever they fit. From there, ReactOS (at least) can drop all the mess of win32api headers there is now (i.e. the stuff in \include like structs.h and friends and the WINE stuff) and switch to w32api full time for the entire project.