yeah that area on the upper door card would be a nice location for the mid (better than a pillars).The only space I see to get close to the midbass is the kicks maybe. To the side is leather plus it'd be firing into the seats basically.
I like the wide open space I have to mount the mid on the upper door card but I would worry about spacing my drivers so far apart from each other. It seems like a pod to mount the tweeter and mid in line with each other would be ideal
And the tweet in the sail panel is close by. Plus the mid isn’t too far from the midbass.