Very interesting what you wrote in your article. Most interesting is how you seem to realize while designing your product that the spreadsheet surface is the most intuitive to users. They like also the baked results you present quickly. So you can see really the problem of your customer then.

What is really good is to assemble a library of visual queries for the customer. This is a good idea for the reason that many users have the same fundamental types of queries on their data. When finally you have enough of the basic queries that the user can do useful work without programming then you can find a way to customize this yes.

Have you data on how many similar queries customers use? Then you should know how to create the basic set of important operations.