CREATING A WIDTH AUTOMATIC USING THE AUTO SLOT MEASURMENT

If I can create a slot or a circle relative to a plane than why can't I create a width in the same manner.  Why should I have to create additional alignments.   Example: I have a project that has 60 slots most of which are used as datum features.  Creating 120 widths and 60 additional alignments in a program is not practical.  Secondly, Why can't I use the points that make up the auto slot measurement and have pcdmis create widths using those points automatically ?  Something else to consider is that all of these slots are drafted with no parallel sides.