FTM does have a rating structure for sources.
Right click on a source citation on a Person tab of a person. Select "Rate" from the right click menu.
You then have two choices
1) Number of stars you select with your own criteria.
2) Number of stars awarded via what FTM calls "standardized" criteria. You check a characteristic for that source and FTM awards the number of stars.
That said, FTM does not have any structure for analyzing and evaluating relationships between people, which is much more important, imho. (for example, that a person is: ruled out, possibly, likely, almost certainly, certainly, a given relationship to another person.)