I do not think using ALT in a table would be a good idea. I'm regretting that I tied my suggestion so closely to tables. My concern is groups of elements, and providing a way for a screen reader to describe the group as a whole, instead of tediously reading through each one. Although users would still be able to get into the details if they wish.
Tables are merely one way that designers group things visually at present.
Whether this be done by adding attributes to container elements, e.g. table cells, or using META is of less concern to me. The essential thing is to provide this functionality. If we use META we will need to spell out the semantics of this application, as I suggested earlier.