Will they listen?
Will Microsoft listen to their customers, or do a "we know better than you" like they did with Windows 8... and the Office ribbon... and so on? For sure, if you don't need a GUI it's a good idea to not install it. But, really, if the customers want a GUI install option on initial install, just give it to them. There probably are plenty of Windows Server uses where they aren't running IIS, or Exchange, or file or print services (does anyone still print via a server any more?), but some random applications (that "could" run on a version of Windows other than server but either aren't supported, or the site views it as a server task, therefore it runs on server.)