I tried too with RT7Lite Beta but it didn't work... got the same thing as you :| is there any way we could do it the old fashion way? using dism /Mount-Wim?
So i've installed chinese version in VBox and switched to audit mode(ctrl+shift+F3 at the finish of the installation , at the user creation), then i mounted the VirtualBox .vdi file with WinMount, i extracted the lp.cab and modified the first and the UltimateEdition line of update.mum from 7600.16385 -> 7601.17104 ! So i could install Hun LP to vdi this way with DISM. I started the system again and switched to Hungarian and I've removed the Chinese language. And then i captured the image to install.wim with gimagex , THAT'S all ! SO it's very complicated, but working fine ! Only the WU page is empty !!!