Withdrawal: An anomaly is that if you select an action, the game allows you to then cancel/change it, except for 'Withdraw'. If you select 'withdraw', to look at the available hexes to move to, and then do not proceed to activate that move, the unit will still withdraw during the resolution phase. I was surprised several times when units made an un-commanded move back, until I realised that I had been exploring 'withdraw' options for those units, even though I had not actually set a 'withdraw' move.
When you explore the 'withdraw' options for a unit (check the highlighted hexes available for a move), then move on to look at other units without activating a withdrawal order, if you return to the first unit to check withdrawal options again, you find less hexes highlighted than on the first check. Just guessing, but has the game allocated fuel for the withdrawal move even though you haven't actually activated the order, so now there is less fuel, fewer hexes to move to, when you do the next withdrawal check. I need to run more situations, to see if there is any pattern in this behaviour.
I have put more detail on this issue in Tech Support : tm.asp?m=4318064
ZOC : the manual states that ZOCs are important in this game and so they are, with the AI demonstrating that it is fully able to set up a defence line with very few units, but making good use of interlocking ZOCs. Unfortunately the AI can become trapped in the same web of ZOC, by allowing itself to be encircled too easily. On many occasions the AI made a good job of using well timed withdrawals, just before a major attack was to be made, but on other occasions it crowded units into hopeless positions, which were too easily cut-off. The AI was placing great importance on holding ports, which is sensible, but went into over-kill risking far too many units, to be pinned against the coast and destroyed.
Historically, I think the Germans found it much easier to slip away, after holding ground, and maybe there is some fix which can moderate the effects of ZOC in these situations, after all the Axis knew the ground better, as they had been in occupation for sometimes months, whilst the Allies were always moving into the unknown, to some extent. I think what I am suggesting is moderating the effect of ZOCs when hexes are, or have been, your own territory.
It is more likely that a side can exert control over a hex that has been in its ownership, by demolitions, booby-traps and stay-behind-units, etc., than a side can exert the same control over a hex that it has never previously occupied.
Could there be a feature where by selecting a unit and pressing a hot-key, all the hexes where that unit exerts a ZOC could be highlighted.
Is there a case where units from opposing sides can exert a ZOC over the same hex and should the side which has ownership of the hex take priory in ZOC.
Supply : Was playing as Allies because the Allied side has the initiative in this campaign and has the most decisions to make, where to land, what to land, when to land, etc.. For the Allies, supply is always short, which is historical, especially when the D-Day landings start to claim most of the available Allied resources. You find that you are fighting supply problems, rather than the Germans, but getting the balance between fuel and supply is difficult and mainly a matter of guesswork. An unexpected breakthrough may require larger amounts of fuel, which you haven't prepared for, because you were prioritising supply for a big battle, which hasn't happened.
There was an issue with the supply levels from the larger ports of Naples and Taranto, which seem to be able to bring large swaths of territory up to 100% supply, regardless of terrain and roads. It may be WAD, but I thought the supply effect from these ports was too strong, so by juggling the number of port workers allocated I kept Naples, in particular, at 50% capacity which seemed to restore some balance, but this is a personal preference.
The AI is never going to be as challenging as a human opponent, although it did show me some tricks from time to time and was able to punish mistakes. Overall, as with this supply issue, keeping the Allied side realistically constrained, ensures a more challenging game against the AI and if it becomes too easy, there is always the game balance preference to favour the AI side.
Disruption: only became a significant factor during one period of the campaign and I think that it should have been more of a feature, with units building up more disruption after combat and not just weather and supply effects, important though they may be.
Fortification: Fortification v Digging-in, Axis fortifications spread like a rash all over the map (only the Axis can fortify) and needs more coherence and should take longer to prepare, with bigger defensive effects.
The current game handling of fortification looks more like digging-in. It can happen quickly after the unit has been in a hex and doesn't seem to play as decisive a role in combat as it should. The current game routine could be seen as digging in, which the Allies could do as well, with a deeper fortification routine taking longer to achieve and giving more defensive benefits, as befitting the construction of concrete prepared fortification, which would take longer than a 4 day turn to have effect.
The Axis AI is spending a lot of its resources building fortifications, seemingly at random then not making much effort to defend, while it is legitimate to fortify cities, especially ports, other fortifications need to be linked to be effective, so could the AI be encouraged to build fortifications linking across the peninsular. If digging-in became a feature, that would be random depending on where units stopped. Maybe a 'digging-in' feature could be extended into fortification, if the hex remained occupied (would it necessarily have to be the same unit) for more turns and more resources were expended.
Terrain Rough/Hills : I think the game has transposed Hilly for Rough terrain in all text references. The map looks correct in the display of terrain and the figures being applied look correct if the terrain names (Hilly/Rough) were simply reversed in all game Manual text and in-game references. I have adjusted my copy of the map mod, changing the 'Map Legend' to show what I believe is the correct order of terrain features.
This is how it should look :

Air superiority and landings : All is ready for an amphibious landing, but the available beaches don't light up and I suspect that this is because there isn't the required air superiority. Which is OK, this can happen in reality, but a message to indicate why the landing cannot go ahead would be useful. It would be unrealistic to know exactly how much air superiority you would need, as you would never know what the enemy air reaction would be, until the event. They might send up all their planes, or none at all, it's air superiority potential that is being measured, but if the 'Amphibious Landing' feature cannot be activated it would help to know why.