OK, if you grew up listening to progressive rock, you have this ailment... you walk around hearing time signatures like 9/4 in your head! Now, you can easily set Metro to lay out the bar lines to any time signature you want, but when you have more than 5 or 6 beats in a bar, it gets to be a bit hard to see where the beats are because the bar lines are so far apart. I've done a few songs where I laboriously went through and changed every other bar to 5/4, so that the pattern of alternating 5/4 and 4/4 bars gives my my 9/4 signature in a way that is easier to see.
So you can guess where I'm going with this... how about a dialog box that would allow the user to lay out a repeating pattern of bars of different time signatures, in order to build up that next song in 19/8?