I share your annoyance! But unfortunately I also don't know how to add a base name and make it work. Some thoughts though:
Adding a litle sound file to the utf file is not the problem; create it in a text-to-speech program; convert it to the same format as the original voice-sound files; create a new node in the utf file and import your sound file to it. Of course, it will not be easy to make the voice sound exactly like it's the person from that utf file, but'I guess it's possible to come close. (A very, very, very elaborate way would be to replace all voice-sound files with new ones that include the names of all your new bases and systems
)
BUT - how does FL know when it needs a certain voice-soundfile? Apparently, as you point out in your example, we hear "Freelancer Alpha 1-1 This is __ you are cleared for launch", indicating that there is a way for freelancer to know what voice-sound file (containg some base's name) to insert at the __ .
Possibly FL uses the strid_name of a base or system (in universe.ini, e.g. strid_name = 196766) as a reference to what sound file it should use. It might be the case that the nodes names in the utf sound files, like 0x803000CA, are an encoded form of the strid_name?
Well, I'm afraid my post ain't even close to an answer to your question, but I think this subject deserves more attention. Especially from a genius guiding us through step-by-step