Perhaps you could briefly post your experience with Factory Fortresses? Though it requires a certain investment in time and money (expansions necessary to play it) you seemd to agree with me that it's a lot of fun and balanced.
I'd say it doesn't get much more balanced than this. The many variables mean that wildly different outcomes are possible, but I like it and find it satisfying to play. With 12 Rounds and a fairly complex map, this needs a little more time to play than other scenarios. Players should be advised to study the map carefully and really look at the special rules for terrain. Once committed to a flank, vehicles cannot quickly switch objectives. In my game, even the infantry reached the bank of the Volga only in the last Round.
Regarding the number of expansions needed, in my opinion, ToI needs all the components to be really useful, anyway. The rules still need cleaning up, though. AT guns are not vehicle targets. AFVs did not shoot at AT guns with AP rounds, they fired at the gun crews with HE rounds and MGs.
I am now in the process of familiarizing myself with "I Ain't Been Shot Mum!", which is the same time and space scale as ToI, but better designed with more command and control and hidden deployment / movement. It is easily adaptable to hexes.
Therefore, my time for playtesting is limited, but you can send me the scenario and I will certainly read it.