Trend Lines (Line from Column Values) with Categorical X-Axis Merged

We have a need to track trends (A percentage) in a P-Chart format with a categorical X-Axis (Fiscal Work Week).  There are 4 limit lines (P-Bar, 1-Sigma, 2-Sigma, 3-Sigma)  That need to be plotted.  In this case the curves are not flat horizontal lines and therefore need to be generated with "Line from Column Values".  Unfortunately this can not be done with categorical X-Axis.  The only workaround I have found was to plot the limit lines using custom expressions, but this makes the lines look like data which is not aesthetically pleasing and is also confusing to the users.  Attached is a DXP to illustrate the issue with 4 different visualizations.  From my perspective there are 3 paths to close this gap in Spotfire functionality:

• Allow use of “line from columns” when X-Axis is a categorical variable
• Use a numeric axis to generate plot, but then mask the x-axis labels from the categorical column
• Allow formatting the look of each line on a line plot. If we could hide the markers and change the line style to dashed lines for the P-Bar and Sigma lines then we could create the look and feel that we need

Any of these would solve this specific problem for me, but I think that all 3 options would be useful to have.