You really want to discourage walk-on's don't you.
Of course not -- don't be absurd.
What I want are these things, but they are mutually exclusive:
1. I want more walkons.
2. I want registered pilots to have no disadvantages compared to walkons.
3. I want there to be P-40's and C.202's in the game.
4. I want people who registered for P-40's and C.202's not to be at a disadvantage.
#1 means, let walkons fill any open slot.
#2 means let registered pilots fill any open slot. If you don't, then walkons are getting a better deal than registered pilots.
#3 means you need to put people in P-40's and C.202's.
#4 is one of the biggest problems. If you let people switch out of P-40's and C.202's, there aren't going to be many people left in them. The heroic pilot who registers for P-40's or C.202's will be left with himself and a buddy in those planes while everyone else if flying 109's, 190's, P-38's, and Spitfires. He will go "screw that" and either want out himself or be unhappy.
I've never flown in any scenario where every registered pilot made every frame. Never.
Me neither.
Those spots were most often filled by walk-on's.
Yep.
It's never been a problem in the past so why is it suddenly such a big issue now?
If by "it" you mean "dearth of pilots in less-popular planes", then, yes, it has been a problem many times in the past. Most recently, in the previous scenario.
It is always an issue. Some Scenarios don't worry about it, and you effectively end up not having the less-popular planes in the conflict. Some Scenarios use other methods.
In this 12-hour format, we will get larger variation in player numbers over the course of the event. Some of the techniques used in 4-frame Scenarios won't work in this one.
Again, 2 choices:
1. Let everyone fill in open slots.
2. Keep registered pilots in their registered planes, but allocate walkons to P-40's, etc.
The usual way is #1.
I think that will result in no P-40's and C.202's for most of the event, and maybe they should then just be deleted. But then we are into designing Scenarios that are far less historical, and we are just going to use the dozen or so l33t rides of AH.