'measure numbers every system' option should number first counted measure
If the first measure in a system is excluded from the measure count - for instance, a pickup - the default 'measure numbers every system' option will not place any measure numbers on that system.
This seems to me to be a behavior people will normally not want; if people ask for the start of each system to have a number, they normally want a measure number on the first counted measure in that system. For instance, when the line has a pickup, put a measure number on the first full measure, after the pickup.
I can't imagine cases where the present behavior would be preferable, but that's because I don't exclude measures from the count except for pickups. If there's some other important use for excluding from the count, perhaps those people like the present behavior and would like to keep that option. But I think the default behavior should be for the 'number every system' option to actually try to put a number on every system.