Who said the combat engine was already abandoned for WitW? The only thing I recall reading was that is the foundation on which to further develop the next engine.
ORIGINAL: Uallas
What I do suggest as a possible method for dealing with the problem of 1941 counter-doctrinal Soviet flight, is that units remain within a given area (military district) until a given date. Ending a turn (or two) outside of their military district would result in losses and/or destruction.
Is this just a 1941 problem? In other words, it isn't relevant if you start in 1942 onwards?
This isn't just a 1941 problem. In fact, I don't see it as a problem at all. It is also not just Soviet related. Also many Axis players withdraw slowly during Soviet blizzard or later summer offensives to prevent deliberate attacks. I mainly attribute it to a combination of hindsight and learning effects, the small gains from holding anything except major cities or good defensive terrain, and the absence of more or less sensible, purely political "soft-factors" (like Stalin's holding early aggressive holding and counterattacking orders, or Hitler's no step back stance including strongpoint formation).
The catch is only that it probably has the biggest impact when one side is vastly superior to the other in terms of fighting power and mobility. Such as the in 1941 when Soviets are toothless (especially with 1.05) compared to Axis, and I bet the more AARs get into 44/45, the better the chances the reverse case will occur.
People complain a lot about that in case of the early Soviet withdrawals, fighting or not, since the Axis player's gains from improving on the German historical mistakes in the early phase are rather limited as the Germans did already quite well. They can gain more terrain at lower losses, including Leningrad a sure given and Moscow more often being seriously threatened now, but the Soviet player has much more potential and gain from not repeating historical mistakes. He can husband his forces for later war knowing that terrain won't matter as long as he just fights to evac really critical industry (again knowing from hindsight which that is; however, also the Soviets did prioritize as well), and he won't fight the many desperate and bloody counterattacks that the Soviet's did historically (which is partly a lack of the IGoUGo being too static and not accounting for reaction during a static phase and meeting engagements etc as well as the players knowing how weak most Soviet units are, both by game terms and by hindsight, and how little to expect from counterattacks).
If the Axis player just doesn't make the mistakes of the Hitlerian strongpoints, i.e. doesn't allow his units to be pocketed much in cities, withdraws too weak forces early instead of fighting for every inch, and doesn't clean his leaders of promising but not Nazi-compatible candidates, there is also a huge potential for improving on Axis mistakes after early 42.