Scatter plot was an excellent idea. Was struggling at first, since the aggregation led to one blob in the report, the sum of account balance and average of interest rate (as per the aggregation rules in the Infomap).
When I discovered the "Aggregate or Detail" option in the data section (would be nice to have this for individual report elements too) everything was much better, and the scatter plot gave us pretty much exactly what we wanted 🙂
(We are, as you might be able to derive, following the "trial and error" approach in devicing our system)
The deciles is best solved in the datamart, and DI Studio is not my friend today (well, to be honest, it never is) so I'm strugglig a bit with the approach. Would like to build the code directly in the Table Loader in the mapping step rather than a custom code step, but guess I'll get there in the end!