Yeah, I'm down with /opt/ too. The empeg installer could drop a symlink from /opt/appname to wherever it puts the actual subdirectory. Then the preinit scripts don't need to be custom, they can all go after /opt/appname/name_of_binary. IWBNI the installer provided good "default" places to put the apps in a dropdown box. I suggest the following:

/drive0/appname (default, since a lot of people seem to want to use the music partitions)
/drive1/appname (for those who ran out of space on /drive0)
/usr/local/appname (my preference, since I have a separate /usr partition)

For those with a non-standard location where they want to physically put the directory, they could just type that in or put it in the installer's INI file or something.