I know a tax lawyer who uses stuff like this, apparently just with Microsoft Excel, including recursive references (Excel throws a warning for this, but they ignore it). I don't think that crippling the functionality of the software to force people into using code is a good idea. Better to enhance the spreadsheet metaphor to make it work better.

This ideally would include some kind of understandable version control (git has a lot of usability issues, even for programmers), and a better module system (right now they just copy and paste complicated calculations to reuse them for a new client).