Hey, I like that idea so much I am going to put it in a year ago
if you write:
MESSAGE_SE = "Cursor", 40
THen it would set volume to 40
similarly:
MESSAGE_SE = "Cursor", 60, 90
would set filename to "Cursor", volume to 60, and pitch to 90.
The same goes for setting it from in-game
$game_message.message_se = "name", volume, pitch
$game_ats.message_se = "name", volume, pitch
You don't have to set all three though, as volume and pitch will default to 100 if they are not set.
As for the message window to appear where it is best suited, I suppose I could work something out for that.