Showing a metric regardless of Dimension

i’d like to display a line graph of a metric that had Dimensions added at some point.
it appears that once the metric had Dimensions added, the query that did not specify a Dimension does not show the metric (and vice-versa).
i’d rather not have two queries - one for the metric with Dimensions specified, and one without Dimensions specified.
losing the ‘historical’ metrics (the ones without Dimensions) in the same graph would be unfortunate.
creating a third metric (a combination of the above 2 cases) might be a solution, but wanted to put this out there to get some thoughts, if anyone has any.