Over the weekend I have been working on some code that does the following. No more grading up to distinction. You can miss out levels, i.e. if only have D and no P or M you will get D if you get all the D, If you only have M you will get M if you get all the M. Here is the part of the actual code that does the processing. It looks like there is no obvious way to have settings values for advanced grading in Moodle admin interface without modifications to core. Please reply here if you would like me to put this into github for testing, it seems to work for me. Feel free to comment on the logic (or elegance).
/* $levels["letter"]==1 means that all criteria at the level letter has been met
X indicates that there are no criteria at that level. $levelmet is the overall
* grade achieved. You could make an argument for additional grades to indicate
* if the overall grade means every available criteria has been met, e.g. PAM,MAM and DAM
* for Pass (all met), Merit .....
**/
$levelmet=REFER;
if($levels["P"]==1){
$levelmet=PASS;
}
if(($levels["P"]==1)&& ($levels["M"]==1))
{
$levelmet=MERIT;
}
if(($levels["P"]=="X")&& ($levels["M"]==1))
{
$levelmet=MERIT;
}
if(($levels["P"]==1)&& ($levels["M"]==1) && $levels["D"]==1)
{
$levelmet=DISTINCTION;
}
if(($levels["P"]==0)&& ($levels["M"]==1) && $levels["D"]==1)
{
$levelmet=DISTINCTION;
}
if(($levels["P"]==1)&& ($levels["M"]=="X") && $levels["D"]==1)
{
$levelmet=DISTINCTION;
}
if(($levels["P"]=="X")&& ($levels["M"]=="X") && $levels["D"]==1)
{
$levelmet=DISTINCTION;
}
return $levelmet;