For one, I believe the possibility of an early German invasion of USSR in 1940 must be kept alive, as it keeps the Allies play honest and focus on the main theater of war. In the previous game, not knowing what was to come, H spent much of his Navy and resources in the Mediterranean while practically abandoned France, coupled with good weather every turn (I know this because both my Tac Bombers were not upgraded, as they've been flying every turn), allowed me to take France in February (never done it before), which means it's game over.
I'm sure everyone can see that the whole war is a race between Axis finishing off Russia and USA getting into France. Every single move of either side should focus on that, and everything else is secondary. If UK put all of her efforts into defending France, including maybe losing 2 out of 3 BEF units, then it's quite feasible to hold Paris until May. Remember UK has 6 carrier attacks, 2 strat, and 1 Tac at her disposal, plus the many allied armies on the ground. Should any German army finish its turn in the front on clear ground, with a strength of 7 of less, it can be finished off by the Allies. Sure the allied planes will suffer dearly (and so does the Luftwaffe), they can always spend the next turn reinforce and be ready again. Also any German units on the coast will have its morale completely destroyed by all the allied CA/BC/BBs. For that Germany has to be advancing somewhat cautiously.
Now that May becomes a somewhat critical date, as Russia can annex the Baltic states early June. Sure Germany may send a detachment to take Lithu and Estonia before that, but that may allow France to hold even longer, and that will be risky for Germany, since USSR will be highly mobilized for multiple turns.
Should Germany be able to launch an early 1940 full scale invasion of USSR, it's game over. Germany doesn't really need the additional tanks and Hun/Rom units, as the Russian units are so weak at this time even German corps can walk all over them.
I don't think an early Sealion is too much of a concern. For the Axis, why take an early gamble when you have a safer way to win. For allies, there are so many corps around the world that can be shipped to UK quickly, defending against an early Sealion isn't that hard, even with majority of BEF destroyed (one should always be able to pull the HQ and the planes back).
Mediterranean and Italian N Africa is quite secondary, let alone IEA. Axis should know even if they lose Italy, they can still win, easily if they defeat Russia quickly. For that allies might actually want the Germans to come to N Africa. Since the allies can choose when to seal off the INA ports as you please and can ship anything from around the world to Egypt, it's really a place where the Allies want to bring the fight to, and I hope the Germans are smart enough not to come. Only if they see there is no quick victory in Russia and Italy may collapse too quickly...