UPK files contain different data, textures, models, materials or animations, and are opened by different programs, what do you need?
for animation And to try to remake all windows
I raised the issue with animations a long time ago, no one could give an answer.
And the interface is a texture, it can be repainted, decorated, but it is not possible to change the windows, because this is not a function of the client, but of the server. It's my opinion!!
but there is no application that we need to edit the locale