Wow - I have a lot of questions to catch up on. . .
I would say 'yes' for the transport plane being allowed to be counted as one of the air units. I will clarify in the rules. I don't eant to penalize the Russians for an early France fall and not having enough aircraft to meet the requirements.
I was also thinking of changing the requirements to 6 ground units + 1 air unit in each of the 5 Polish/Lithuanian territories plus add Bessarabia to the border requirements. It is feeling increasingly odd to me that Bessarabia is usually undefended by the Russians in our games. By decreasing the ground requirements to 6 and adding another territory, we would only be increasing the total border requirements by 1 ground units (and one air unit). Let me know what you think.