Interesting idea! I know that Michael said doing in-line calculations/variables should not be too hard, and they would consider it. I am curious if you can provide a more typical-Fibery example use case for the functionality you’re describing.
What came first to my mind, though it may not be an example of what you had in mind (and may not be that useful, or the best way to handle it), is a “CSV Import” block, which basically shows a spreadsheet-like view of a specified CSV in-line on the page, and then allows you to directly reference those values elsewhere. This is advantageous over the much heavier current approach of importing CSV data into some Type (or creating a Type for it), and could help address some of the various requests around here for more ad-hoc data handling. It’s a half-formed idea, but I’m curious if this maps at all to what you were contemplating. And certainly I’m interested in other examples if you have any.