You probably shouldn't have gone into legacy boot mode to begin with, but UEFI is a stupid mess of a solution seeking a problem. That said, nearly every modern OS has a way you can boot it from UEFI, including GNU/Linux-based systems. You should have worked with that first. More info
here.
As for what to do from here, I don't know what to tell you. UEFI is too new for my expertise, so my old advice, like loading a BartPE environment or something, probably won't work now. If there's a Win8 equivalent of BartPE, then maybe try that.
This whole UEFI thing is symptomatic of a larger problem. We're so up our rear ends about finding "new" and "innovative" stuff that we start throwing out stuff that works well, maybe with a few fixable problems, in favor of the new shiny just because it's the new shiny. Like systemd, for example. That's not to say there aren't software projects that NEED to be made obsolete, like X, but all this going to new stuff just for the sake of going to new stuff is absurd. There's nothing BIOS was lacking other than a shiny, mouse-enabled UI, and that's something that could have been done without introducing the whole new fail that is UEFI, maybe by extending BIOS slightly. And don't get me started on secure boot. Stupid, stupid, stupid.