It may help to expand on your proposal. For example, what do you mean with group by, but not summarize? The group by clause says nothing about how to combine data not in the group. That has to be on the select. And I have yet to find a solution that beats ROLLUP for giving a great overview of data.
About the only thing that sucks on the current syntax is that it is not possible to get auto complete in the select, without having some from.