Several Jets DLC aircraft have separate textures for their ID numbers so they can be modified without a full retexture. On the Shikra and Black Wasp II, these textures are configured as hiddenSelections, making it possible to change them using setObjectTexture.
The NATO UCAV Sentinel also has these separate textures, but they are not configured as hiddenSelections. As a result, it's impossible to change them.
The textures and selections already exist; hopefully fixing this is as simple as hooking them up to hiddenSelections and requires no awkward asset changes.