With so many more tanks and tech trees, a possible idea to keep track of what your must obtain tanks are would be to implement a wish list whereby tankers could right click a tank in the tech tree and select 'add to wishlist'. This would add a symbol to the tank in the tech tree so you can easily identify what lines you need to research.
Further to this you could always add a popup message when a corresponding 'on track' event occurs to let the tanker know in game that a tank in their wishlist is part of the 'on track' missions.
What does everyone think?