The reason I asked is that I believe this behavior is what Emacs does by default (actually don't know if by default, but saw this from code produced by Emacs users) e.g.

<tab>(inserts 4 spaces)<tab>(replaces 4 spaces into a tab that is 8 columns)<tab>(adds 4 spaces after the tab)<tab>(replaces with two tabs and so on)

Unless I misunderstood what formatting you were using.