The short answer is that we found interdiction to be too powerful in a game like FITE2 - at least at phases when one side has more or less complete air superiority (early and late game). You take very few losses and the effect on supply and the disruption of troop movement are huge. Especially the effect on artillery is huge: one hit from interdiction and all gun are destroyed in an art unit making it difficult to rebuild any kind of line. For instance, we found it impossible for the Russians to get any kind of decent defense ready at the Leningrad front before the Germans arrive.
I agree it is unrealistic, and I would love if it could be implemented. We tried other options (for instance that each side could have a fixed number of units on interdiction) but decided to go with the complete ban as it is easier to administrate.
You should feel free to lift the ban if that works better for you. A huge game like FITE2 is difficult to balance, and the way I and Søren play may not be like other people play.
Anyway, we are very happy with your input and hope you enjoy the game.
With all the other effectiveness sliders added in this release maybe it's time to lobby for interdiction to be added to the list.
Did you ever see history portrayed as an old man ... weighing all things in the balance of reason?
Is not [it] an eternal, imploring maiden, full of fire, with a burning heart and flaming soul, humanly warm and humanly beautiful?