I don't know what the limitations of the arenas are... I thought I heard at one point that winds can only be deployed at even thousands of altitude, for example, and that's why the downwind was set at 16k instead of 15k.
Assuming its possible, I'd suggest having the full downwind at 16k, half that amount at 14k, and half again (one quarter) at 12k. Then let people decide for themselves if its "worth" going above 12k or above 14k.
Or to make it simpler, just have the full downwind set at 14k instead of 16k, and let people fly at whatever alt they want. Most will probably fly at 13.9k, which limits their upward mobility... but so what? Its better than thinking the other side is cheating when you see someone up that high.
About aircraft selection, I definitely think it was a good idea to go away from historical planesets in order to assure that people will actually sign up for both sides. As it was, the Axis were plagued by no-shows, and we didn't have our intended ratio of aircraft. I think it was in large part because people weren't interested in flying A6M2s. Historically, I suppose the scenario designers "should" have made it into a "turkey shoot" for the Allies, with hordes of sub-par Japanese planes in the air so that every Ally pilot could become a scenario ace. But lets face it, that's only fun for the Allies.
Another problem I think started from re-opening registration a couple times. I think this really diluted the players that would take it seriously enough to show up all four frames with people that just wanted to have a spot reserved, even if they could only make it once or twice. I think it also made it so that there wouldn't be enough walk-ons to fill out the rosters. I think a scenario should have a designed of pilots for each side and not get expanded. Maybe after that make a "preferred walk-on" list if there's the demand. But a scenario that has the numbers skewed one way or the other instead of the correct ratio thanks to no-shows and not enough walk-ons has a serious problem.
That's all I got, Rangoon '08 was my first scenario and it was a lot of fun. I probably won't sign up for BoB because its football season and the dates will certainly conflict with tailgates / home games. But I hope I can at walk-on to one or two frames at least.