Did you know you can get a 2nd y-axis on a chart? This can create what some people call a mixed-series chart, with a combination of bars and lines.
If you add 2 measures to a Bar Chart, one of which has "normal" numeric formatting, and one which is formatted as a percentage, PerformancePoint will draw the % series on the right axis.
For example, here's a simple chart with one bar series.
Add a 2nd measure to the query, and if it's a percentage, PerformancePoint will automatically add it to the right axis. That's it.
Note: Be sure to add your percentage measure as the first measure in the Series, that way the lines will draw on top of the bars. If the percentage measure is second, the lines will draw behind and may be hard to see.
We don't have a way to manually control this yet, we are hoping to add that in a future version, but for now, you can create mixed bar/line charts as long as you're using percentages.
Senior Program Manager - PerformancePoint