[dragonwriter]

What if instead of "propagating empty cells as #NA everywhere", instead the functions operating on cell values returned #NA by default if an empty cell was present in the input, but also included an optional parameter which was either a true/false flag to treat the value as the appropriate identity (makes sense for things like SUM, etc.) or which provides a default to use in the case of an empty cell (which may make more sense to use for functions that aren't the append function of a monoid.)

(Though I think the failure to use exact arbitrary precision numeric values except where an imprecise operation forces fallback to limit precision binary floating-point approximations -- and then visually distinguishing when the latter has occurred -- is a bigger problem for common spreadsheet use cases than the bad null handling.)