Adding that code to the *.Target.cs files didn’t seem to change the WINVER value, it stayed at 0x0600.
I found a workaround by changing Engine.h to include the Macro and that seems to have done the trick, but that involves changing Unreal Engine’s Source itself, would be nice to have to avoid modifying the engine’s source.
//C:\Program Files\Epic Games\4.10\Engine\Source\Runtime\Engine\Public\Engine.h
#pragma once
#define _WIN32_WINNT 0x0603
#define WINVER 0x0603
//Rest of Engine.h...
I was able to initialize a touch window, hopefully this could evolve to become a multi-touch plugin for Unreal Windows 8 in the future. Thanks for the help!
There was also this question from earlier which was very similar.