It's pretty arrogant to complain about the syntax being inconsistent across versions and databases and then present your own weird offshoot, as if every other version wasn't introduced for the exact same reason with the exact same lofty delusions of grandeur...
SQL is messy because describing the underlying data relationships are messy. The orthogonality example is a great illustration of this. What exactly should the result be if there are multiple dept heads? Should the result rows be duplicated? It's not clear how edgeQl would handle either (their edgQl orthogonality examples were constructed to only have result per sub query), but it seems like they would be kept together as sets. In that case, the result set is no longer a table, it's a dataframe, which is a useful data structure but is also not what relational databases do.