A typhoon would be pretty hard to tell from a tempest from 3 miles away.
Once you get up close it would be a little more distinguisable... say, I dunno, maybe a half mile or so?
Oh wait, that is the system they just implemented.
Anyway, the only planes this really affects are the *really* early war planes (like the Spit I and Hurri I), and the LW planes.
The rest (P-47D-11 vs P-47-D40 for instance) perform so similarly that plane X will have the same advantages over the D-11 that is does over the D-40.
I can see the Spit 5/ Spit 9 possibly being affected since someone in a Spit 9 isn't going to turn with someone in a Spit 5 as readily as he might have turned with a Spit 5 wearing the Spit 9's skin (pre-icon change), but that isn't going to be a huge great deal since one of them or the other will be busy dealing with 2-3 more bad guys to really concern himself with the nuances of Spit 9 vs Spit 5.
Wotan makes a perfectly valid point about grabbing a 109E and rolling into a fight with it... it isn't (well, wasn't) a bad choice. Firepower is decent, it turns a lot better than the other 109s, and you have an opportunity to get close. When whatever plane you finally get saddled up on looks back and sees "109" and turns (because 109s can't turn, everyone knows that), the E could slide in there for a kill. Now, when someone looks back and sees "109E", assuming they don't go "WTF is a 109E?" they'll just level out and leave.. pretty much any plane will dust a 109E. It combines none of the strengths of the other 109s (climb, acceleration), with subpar "strengths" that are done much more effectively with another choice of plane (turning).
To be quite honest though, less than 1/2 of 1% of the kills in the MA are made by the types of planes that will be affected negatively by this choice. So they basically already don't exist (in the context of the MA), so there is no downside to this move.
Actually just played with the numbers... out of 324,496 kills made by fighters in tour 60, 1,933 kills were from what I would term "early war" planes (Spit I, Hurri I, 109E, 110C, A6m2, F4F4). Came out to .6%, or just a bit more than 1/2 of 1%.
For anyone who is interested, the total for the LW planes that I think will be negatively affected by the move (109F-G6, 190A) came to 26,413 kills, or ~8.1%