I think it would be good new feature to choose from two optional ways of shortening interface bars.
Now bar is omnomnomed from the zero position and moved towards it (see fig 2 in attachment). The new, choosen in Interface Maker way would able us to make the bar omnomnomed from the end of it (fig 1).
Since I started interface modding I was freaking annoyed, that I can't do some awesome effects because of this way of work of bars. Really! It can halp modders in making even more awesome interfaces!
Second thing - "god dmanit, why tis fukced Jet Bar is on top of intreface layerz?!". Maybe moddable hierarchy of layers? Pros are the same as above...