When running an app that is not already defined as a launcher icon under the Dash icon, a new icon always pop up at the bottom of the vertical string of assigned icons. Is it possible to make the newly active icon pop up under the Dash button, so new active program icons are on top and not the bottom of the list?
The launcher gives you keyboard shortcuts to switch between windows. These are dynamic and based on the launcher position. If Nautilus is the first item, for instance, then you can start an instance or switch to an existing instance by pressing super+1. To display all open Nautilus windows, you'd then press super+11. (one one) In order to open a new instance, even if you already have one, you'd press super+shift+1.
Once you get used to them, these are extremely efficient keyboard shortcuts. However, if you placed new applications at the top, then the keyboard shortcuts would also be random, which would remove all the benefits. Another thing is that you may fill your launcher with more entries than it can display, in which case the lowest entries will be compacted or run out of the screen so you have to scroll. You probably wouldn't want your most frequently used applications to become less available.
Adding to the top would also create two different groups of entries; the locked ones (the most frequently used) and the others. If you then decided to lock an entry to the launcher, what should happen? Should it be moved to the bottom of the list? And if you unlock an entry, should it be moved to the top of the launcher, or to the bottom of the unlocked entries?
For these reasons – and I'm sure there are more – I think it's highly unlikely that your idea will be implemented in Unity.