I'm actually going to be keeping a look out for bit fields in the datafiles. The field in unitref for determining flight ability is also used for kneeling and one or two other things that escape me at the moment (the toggle for the kneeling leg sprite being one of them) (also the visibility field in unitpos.dat is used for the mind control status - that's definitely a bit field). Most of the rest of the fields are apparently filled with garbage bits (since they aren't always the same from game to game). Rather clever, when you think about it, as this can cause the same value to be wildly different from game to game while at the same time produce similar results. Quite clever... even if it may have been accidental .
When I'm free, I'll have a peek at the objects in obdata.dat and see if it has any bit fields in it too.