Default wow UI is anchored left to right, grows upwards when more rows added. It'd be nice for a mirror/right anchor to be added. Also the extra rows to grow underneath. This is just the horizontal bar view.
This image is a poor photoshop jobby btw.

Here's a link to the wow forums where people are asking for the same thing but this thread mentions vertical mirroring.

Since currently i am setting the anchors manually (hard coded) it should be possible with some code to make sure all buttons are oriented th correct way afterwards.

Still might take some time since on DF launch i'll don't have much time for the first week :D

Bonus image for you, mirror flip AND growth change.
If you do decide to do this, that would be great and I'm sure a lot of people would appreciate it other than myself who don't want to install the whole UI package dominoes/bartender offers.
Thanks!

Another question coming to my mind... Wouldn't it be enough to be able to configure mirror vertical and mirror horizontal on each bar?

Since for example mirror vertical on a horizontal bar would lead to the bar growing down. If you then would want to flip the sides you'd have to enable mirror horizontal aswell.