Hi I.S.
I have not added you patch as it is, because in some ways the syntax
it adds is
questionable, and, as others have pointed out, sorting can be done in
different ways, too.
However, instead, I have introduced a variable that can be set to a
user-defined function to compute the base priority of a node. So you
can simply put your function into that variable and continue to use
your special syntax, with us making it an official Org syntax.
The name of the variable is org-get-priority-function.
I hope this helps.
- Carsten