This is likely neither pretty nor practical, but maybe it can give an idea.
Also there are probably ways to do this inside Tableau with domain padding,
but in the workbook attached in the Forum Thread, I used a brute force
list of coordinates to generate a circle. I then joined the coordinate table
to the SumPhase values, so that each phase had all the circle coordinates.
Then I scaled the value of the coordinates using the SumPhase as an area.
Lastly, I shifted the circles down to the minimum of the biggest circle.
This method is further described here:
269643circ.twbx 45.6 KB
Thank you Gantela.
This is really useful!