What kind of unbalance do you think ME410 would create?
The 410 won't be added any time soon due to the problems with modeling the gunner position.
The P-39 is a must have for the early PAC and Ostfront theaters for the CT.
(Did 110C-4/B do that in BoB with its N engine? Was it too good against Spits and Hurris?)
Look at the entire LW plane set and you see that any BoB scenario is just some made up of mixed match of aircraft - like most AH scenarios.
The Bf 109E-4 is the only plane in the set that truly belongs in a BoB event. Even then there were large numbers of E-1s and E-3s (many brought up to E-4 standards).
The Ju-88A-4 didn't fly during BoB. The pre-dominant A-1 was slower then the A-4 as was the A-5 (A-4 airframe and A-1 engines).
There's no early Stuka.
Finally, we come to the Bf 110C-4/B which over performs the standard and more common C-4. I was CO for the First AH BoB event and my Bf 110C-4/Bs ended the event with the highest KD ratio of any other plane. I didn't fly the last 2 BoB scenarios, or even check the stats. However, if the Bf 110C-4/B were deployed properly they should have dominated.
The problem with the overall AH plane set in its current form is that from the beginning planes were introduced based on whatever HTC decided to do at the time (cool factor..?) or to fill holes or needs in the main. Little thought was given to scenarios or to anything like the CT.
Even after ToD/CT was announced and 'in development' they introduced an aircraft like the P-47N when an early C model would have been better. They re-did the Fw 190s and an A-3 or A-4 was not introduced and neither was an Fw 190A-6 (an easy conversion from the A-5 - just add 2 MG151/2cm in the wings to replace the MGFF).
Outside of a very basic 8th AF CT every other theater will struggle with stand in aircraft and made up plane match ups.
When you look at the number of rare and very limited aircraft its hard to find any method to how, why and when for their introduction.
Any new plane is better then no new planes - especially in the old main. However, with the changes it would seem that there's the possibility to get away from the wonder weapons and to start filling the holes with more useful and common aircraft. This may or may not happen - I thought the same thing with the announcement of ToD/CT. It didn't happen.