I have a patch in the system for this and I did have to put in a central
"wrangling point", which is basically a very simple event snooper which
sets the Alt flag if the <user selectable (defaults to 1) mod flag> is
set. This user setting is a new option in the preferences.xml file so can
be set differently by each user for their keyboard rather than being
hardcoded in the way the current Alt usage is.