Thank you! It might be a bit too much. The vehicle that I want to build would be an up-scaled version of Vityaz DT-30 (youtube video in first post), with drive wheels of about 1 meter in diameter or bigger. So when you stand next to it in first person, details of the tracks would be quite visible. For the LODs it should be easy to fall back to animated texture on skinned mesh and I can do it even for “hero” tank when speed of the track is just too large to distinguish separate links.
Ohh, now I see that I’ve missed one detail - track elements are Instanced Static Meshes, they should render rather fast and performance hit comes from updating instances with new transform each frame. Which again can be done less frequent with the distance.
I’ve seen one drawing of M133 with top rollers but not a single photo with such setup, most likely it was just a mistake. Tanks with Christie suspension, like T-34 didn’t had rollers, most likely because amplitude of how far up/down wheel could move was so large that wheel could hit top roller.
You are right, it shouldn’t be dynamic on M113, I could make a dynamic idler for something like Ripsaw spring loaded wheel. But M113 and plenty of other tanks need different solution.
P.S. Battlefield 4 got away with so many simplifications, like here wheels are not even connected to axle of torsion bar 
But I’m just being picky, didn’t noticed this before at all.