Hi Stefanos,
interesting question, as some weeks ago I came across the same requirement and implemented several scripts to achieve this. The Axis Scaling in a waterfall chart now works very fine dynamically. Independent of the chart type we use it for all kinds of charts not only for the waterfall chart.
One global script does the chart scaling. You can pass min and max as input parameters to the script: my_chart.setAxisScaling(ChartAxisScaling.Y_AXIS, l_min, l_max);
The min and max values are defined with another script in the „on result set changed“ event of the dataprovider. I use several getdata functions in combination with loops over the columns to find the values. Afterwards I call the first script which does the scaling.
Result like in the screenshot below. When you apply e.g. some filters to your dataprovider the script will be triggered and the chart scaling runs again.
Just give it a try 
Kind regards
Martin