Sorry I was thinking of function fields not calculated fields but on second thought they would not help anyway.

I would probably try to convince the stakeholder to stick to the boxplot. The pivot table is the closest what is achievable easily/OOB or you could calculate the aggregate table in a remote table. It would be simple enough to create a custom widget like above but is it worth it just because one person can't read a graph. Especially when the migration to platform analytics is going to happen sooner or later. 

It's always good to understand why stakeholders are stuck on certain ways of displaying data etc. it might be that you can get them the information they need in a better way.