Wow, strange to choose here the CeSetThreadPriority mapped to Win32's SetThreadPriority. It would be worth to mention the difference in parameters, yet alone the differences in thread scheduling. Ever stopped to think why there is the CeSetThreadPriority API in WinCE in _addition_ to SetThreadPriority in the first place? (and calling SetThreadPriority "modern api", really?).
The bottom line is that anything WinCE or even Win32 is rather not portable to UAP and would end up as big re-architecting exercise for anything not trivial. So why would one choose Win10 IOT over anything else (esp. given experience with support and commitment to WinCE)? What's MS business model here? Is it another "strategic" MS move that may get abandoned/dead ended?
Also, standardizing GUI on ~WPF/XAML implies high res displays and mucho CPU/GPU (vector rendering) => $$$ & power.