Yes, if you just hit save then I think you'll get pretty much an empty file.
I'll think about this one a bit.
The potential to produce a file which'll error is the part which I think is particularly bad.
The easiest way is probably to start you off with a top level HQ there already.
If you hit save and re-load you wouldn't get an error.
OTOH I could disable save options if there are zero units added.
That still leaves hiding and showing some label.