I'll consider it. Although I think a key like HiddenStartingLocations= might work better.
It'd be possible, but I don't want to break maps that already make use of the client's features. There's not many of those, but still.
Because the client was mostly developed based on the different projects' (DTA, TI, MO, YR) needs and I've mostly been the only developer, there is no real documentation. Instead, you can look at the different projects that already utilize the client, or its source code for how it works.