I was doing some research on the guy who designed the stage and it turns out he also designed the stage for Big Bang's Alive Tour.
The layout of the main stage looks identical to Gaga's layout, but instead of the arches you've got the white castle. It's going to look so good with the screen behind it.
But the thing is, it wouldn't be a hologram. Hatsune uses projection techniques that make her look 3D even though she's actually just a 2D image being projected onto an "invisible screen". The technology isn't as advanced or expensive as an actual hologram so it's totally plausible Gaga could do it too.
