I haven’t seen this particular trick out there yet, it’s a fun one for the toolbox. When we’ve wanted to mix and match KPIs in a crosstab or text table, we’ve had to resort to multiple worksheets on a dashboard in a layout container, or a multiple axis crosstab. The former can result in various display issues because Tableau imposes certain border sizes, the latter has problems with performance due to the number of separate queries and computations that are necessary.
Tableau version 8 gives us floating dashboard elements with pixel-level precision for element location, and that gives us a third way to build text tables with KPIs.