Remi,
I like this idea, as it would also reduce wineserver load for raw-input events, since the input should be the same regardless of which x11 thread it comes from.
One issue I can think of however is that we'll have to accumulate raw-input mouse events in wineserver, as in my testing when you send WM_INPUT at a rate faster than the thread calls MsgWaitForMultipleObjects, it causes some very strange behavior, at-least in over-watch.
Also, does dinput really send input at all times, regardless of focus? That sounds unnecessary for games.