Buttton Tags renamed
We, of course will have to wait until the asset lists are released, but the button names have changed.
Since NDA is off now every skin I have tested lost all it's buttons because of the changes to allow you to select which buttons you want. As hypothesized above, the asset names have most likely been changed to facilitate this in-game customization. There will also be a lot of new assets for the various icons for the button choices. But that's not all that drastic. The new primary menu will also contain a chunk of new assets that will require work but there it appears the menu will use defaults if it is ignored by the skin, except for the icons.
The only things I've found consistently broken to unusable are the buttons on the main bar. Oh and that includes the icons for bags.