I have a CH Pro Throttle, so I don't know how this would translate to another stick/throttle, but this is what I did.
On my throttle I have an 8-way hat ... I used it for "auto" flight setting while flying ...
AUTO-LEVEL
not assigned not assigned
AUTO-ANGLE not assigned
not assigned not assigned
AUTO-CLIMB
Now, prior to the new Vehicle changes, I had these key defined in both my CH control manager and in AH "Flight" key mappings ...
auto-level sends -> x
auto-angle sends -> shift-x
auto-climb sends -> alt-x
I wanted to use this same hat for the new vehicle keys (W/A/S/D) so this is what I did ...
In CH Control Manager, I changed the buttons to send ...
W
A D
S
I then when into AH Key mappings and choose "Flight" ...
I changed ...
auto-level to -> W
auto-angle to -> A
auto-climb to -> S
The beauty of this is that Aces High lets you assign the same key to multiple functions across the different modes without any real conflicts ... with the exception of key mappings in "Global".
So now ...
When I am in "flight" mode, when I press the hat to the up position, it sends the W "key" to AH and AH says ... Oh, he is in "flight" mode and the W key means "auto-level".
When I am in "vehicle" mode, when I press the hat to the up position, it sends the W "key" to AH and AH says ... Oh, he is in "vehicle" mode and the W key means "Accelerate".
I used this same technique to also assign the "Gunsight Range Increase/Decrease" to a button on my stick that I use for "Flaps Up/Down" while flying.
Hope this help some people.