Right now, in order to be still compatible with FSX, the Safegates use an set of preset images, so we just cannot write any information that is dynamic in nature (like the assigned gate, the time, etc.).
Well, we could in theory using the same method we used in PHNL to have the control tower showing a digital clock and temperature, but it would be very hard on fps for a Safegate, and very cumbersome to do too.
When we'll eventually release a P3DV4-only native version of GSX, it will be possible to use some very powerful features of the P3D SDK, that will allow to write into textures in realtime with DirectX, as they were an airplane gauge, which will result in more flexible (and even easier to develop for) Safegates, with the ability to write anything into them.
That's one another (of the many) reasons, why we hope users will move away from FSX as soon as possible, because GSX could improve a lot, if we could forego the FSX compatibility.