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Split arena in 3 parts. 
1. Earlywar arena 39 -41 
2. Middlewar arena 42-43 
3. Latewar arena 44 -45 >>  -Mipoikel
I like the idea of splitting a Tour into a few parts, but think it should still utilize the perk system.  For a very simplified example, make something like an ME-109E and F4F-3 free to any player for the first arena setting and have those aircraft that are mid-war or mid-threat have perks at say a 10-30 range and those late-war or severe-threat aircraft perked at 50-80.  Then when we hit the middle stage of the Tour, those mid-threat aircraft would become free and the late-war stuff would drop.  Again, it's a just a simplified example.  But this wouldn't prevent anyone from flying anything.  Maybe an LA7 will cost you a lot during the early-war arena and not so much during a mid-war, but it's free during the late-war arena.  Rolling perks doesn't prevent anyone from flying anything and it also allows a greater chance of survivability for someone who wants to fly the Hurri1 or ME109E or P40 a little bit in the MA.   My $.02.