Note that we should only translate accelerated mouse input to the Windows rawinput (WM_INPUT) messages. Other mouse messages (WM_MOUSEMOVE) should reflect the host pointer acceleration [*]. Currently the rawinput messages are automatically generated from the absolute mouse input -and are therefore always using accelerated values- and there's no mechanism to do it separately upstream yet. Wine staging has one, to implement rawinput on X11, but it's not completely clear to me whether it should be done that way.
[*] At least until we have a Wine-specific mouse acceleration support but that's also another topic, and it's not even clear that we need or want one.