Sorry, for some reason I thought that fonts with the same name would be chosen alphabetically. At least that was what motivated me to purge v1 while finally installing v2 in attempt to make text look sane again after recent fontconfig changes. A faulty memory of some old discussion perhaps.
Never mind then, false alarm. Since all liberation fonts are supposed to be of the same metrics, *in theory* swapping them in Flightgear would do no harm. But you never know with hardcoded stuff.