Back on topic...is it out of the question to ask why the normal 2-life system was abandoned for this setup? Is it the Scenario CM Team's belief that forcing 109's to fly Ju 87's in their second life will help the event? Also, does the Scenario CM Team believe that having a chance at a 1-sortie Scenario as an RAF pilot will improve the event? Please, I am being genuine and seeking thoughts. I am not putting words in your mouth nor am I criticizing. Simply trying to grasp why the radical changes were made knowing the obvious problems with scenarios recently.
The number of lives varies from scenario to scenario. For example, Rangoon, '42, Coral Sea, and Rangoon 2008 were one-life events. Battle of Britain 2004, BoB 2006, and BoB 2008 were as it is for BoB 2013. Stalin's Fourth was based on a number of aircraft available, with fewer pilots showing up meaning more lives for those who did show up. Operation Downfall had unlimited lives. Der Grosse Schlag, Battle Over Germany, and DGS II had 1 life for bomber pilots. How these things (and the other multitude of design parameters) are picked is based on the designer's idea of what will be the best mix of fun, realism, balance, action, etc.
There are some people who prefer single-life events because they feel it adds a lot more realism to the feel of the event. Some folks prefer 2 lives. Some folks prefer unlimited lives. The Battle of Britain scenario design was first made in 2004 by Tilt. This one is geared toward the more-realistic side of number of lives (i.e., 1 if you die your plane as an RAF pilot). However, since there were cases of RAF pilots bailing out and getting back to base, that element is brought in. So, that gives on average for the RAF more than 1 life. On the LW side, you can't do that, as the rescue was less likely and would take far longer to get a pilot back to base; and you have another problem to solve. There were lots of Ju 87's in the battle, but you aren't going to get people to sign up to fly only Ju 87's. So, instead of 1 life for LW fighter pilots, you give them a life in Ju 87's, too, and will solve both those aspects.
It was run in 2004, 2006, 2008, and now 2013. The previous 3 runnings were popular (as judged by several rounds of polling of the players) and well balanced (as judged by the first two being nearly draws). If I see a past design that was popular and balanced, my feeling is that changes should be small except for replacing any substitute planes with the more-correct planes that have been added to AH. I'm not the only scenario CM, so it's not my call, but that's what I'd recommend.
So, in short, BoB is this way because that's how it was originally designed based on designer's feeling of what is best (and not every player will agree); it worked well in the past; and we didn't change much.