JAB,
I disagree. If icons were unique I think you'd get a more "cookie-cutter" approach to fights. As it is, some aircraft in the MA benefit from the presence of more powerful brethern. It buys them some extra room to work effectively and giving them unique icons would damage them. Just think seeing a 190, 109, or F4U's, you don't know exactly what you have as compared to a C202/C205 where you can apply specific tactics based on icon (the C202 and C205 are very different). It's not the more powerful aircraft gaining benefit, it's typically the less powerful ones, which gives them a fighting chance. It would certainly change how you would have to approach combat knowing that you might have a "sleeper" aircraft mixed in or you might only be facing the least capable variant... the unique icon method would lead to "selecting targets in order of capability" vs. just having to deal with the one that's "there" and adapt your own fight to suit what you learn about your opponent (his aircraft, his skill in it, and his knowledge of ACM).
I know that when I fly the non-D9 190's (frequently) I use every asset I have and that includes making people think I'm a D9. It's MA nature to make that assumption and I use that to my advantage.
-Soda