I wonder if ReactOS could target the same APIs as the upcoming Nano Server [1] in Windows Server 2016. They'd have to make it entirely 64-bit and implement some closed Microsoft protocols like WMI and DISM, but it could be a pretty cool drop-in replacement for any server apps that people decide to target to Nano Server.
[1] https://blogs.technet.microsoft.com/windowsserver/2015/04/08...