What do you think of thunks?

I have my prejudices, but I would expect my approach to become stronger.  If, say, XLOOKUP were used to identify first and last cells in each range, then the range ":" operator would return a variable length range for each mapped value.  I could put the search criterial within a Lambda function to modularise the problem and then return the ranges within thunks (ranges, especially of varying size would throw an error within MAP).

I can then perform the calculations on the individual time slices of the data table with a second application of MAP (or, better, a custom version of MAP that expands the thunks automatically before passing the range to the function specified by the formula

MAPϑ
= LAMBDA(ϑ, FNλ, 
    MAP(ϑ, LAMBDA(ϑ, FNλ(ϑ())))
);

The strategy would be to break the calculation into a hierarchy of Lambda functions, each one with a well defined task.  In essence, I propose to use thunks as a 'pass by reference' strategy, as opposed to 'pass by value'.