spotted so far:
Spitfire I (2 Versions)
Hurricane I (2 Versions)
Su-26 (just for fun )
I wish there were more RAF flyables....a Beaufighter lacks the most.
Also, I would sell my soul for a Short Stirling addition some time in the future, as an AI or even better as a flyable. It would be amazing to get to fly something so huge. I know it's not from BoB but if they expand the theatre I really hope to get to see it. And of course the good ole 190.
i personaly miss a RAF bomber that can carry more than ~1000lb of bombs
So for me a flyable Wellington IC (because it is already as AI in release, my very personal favorite in general would be the Hampdon ) is the most demanding IMHO.
Would be 'important' for online events.