My customers are not finance people, but they were using ad-hoc spreadsheets extensively and most of them through G suite. By implementing bidirectional sync for both master data and outputs they have the best of both worlds.
The Google Drive and Sheets APIs (and especially the on-change push notification callbacks) are not a pretty sight but once the twisty maze of nested data structures, webhooks and OAUTH2 and what-have-you were successfully navigated we got an efficient, complete and stable solution that everyone's happy with.
[0] https://support.office.com/en-us/article/Get-external-data-f...
Since it was a system for internal use, that was deemed acceptable.
So that gives the user the ability to query for a certain date, or sum for a date range, or to get a breakdown by some meta data. Being able to load multiple reports allows them to do deltas. And switching to a newer version of the report just takes changing the argument of the load function and press F9.
Worth also giving the users sample spreadsheet, or having a way to export the full report with all these formulas in Excel so that they can learn by example.
The only thing to watch for is memory clean up. You need somehow to have a way to unload all reports otherwise your memory blows up over time.
My Julia code creates Excel sheets including charts and sparks
I use this shiv to Python's XlsxWriter
https://github.com/lawless-m/XlsxWriter.jl
With a bit of effort you can even make it set up scenarios for Excel solver
The smartest thing that I did was make it accessible from Excel. You could build a spreadsheet off of my report. Refresh the spreadsheet, the report ran, you got updated data.
I got essentially 100% adoption, and the rest of my job was spent finding people who needed data and adding it as an option to the reporting system.
Usually you expect a complex reporting system to have features like graphing, pivot tables, etc, etc, etc. My answer to all of that was, "You can already do that in Excel. I could spend a lot of time on it but I'm not going to do it as well as what you already have."