From: Sydney, Australia
Back to China.
The new map is going to have a huge impact. I am yet to play a game of MWiF so I really don't know what that impact is going to be. I suspect that it will favour the Japanese because they can put more units on the ground than China can.
In WiFFE the Chinese player usually gets to play along as best as they can against the Japanese strategy, trying to hold the mountain terrain, until the USA enters the war. At that stage the Japanese player will usually need to start pulling units out of China to man their home country and their new found Pacific dependencies. The Chinese player at that stage can usually make a few inroads into recapturing terrain lost during the rest of the war, especially in the north where the Communists generally have stronger units and a better leader.
If you play with the "Chinese Nationalist Attack Weakness" option, it becomes much harder. China will usually be pushed well back to the last few factories, and quite often conquered (in the 7 games I have seen played with that option, China was conquered 3 times). In the face of the changed map and my past experiences I would strongly recommend playing without this option -- nobody I have ever played with has ever used this option and for good reason because it tends to lead to very ahistorical outcomes.
As the war progresses, it's common for the Chinese to run out of units to build, other than air units and naval units, unless they get especially punished by the Japanese. However there are a number of nice aircraft that the nationalist Chinese can build, especially if they have their pool built up by lend lease from the USA (which is not a bad strategy, because it means that these aircraft can be built directly in the face of the Japanese, rather than having to be shipped from half way around the world). This usually means that the Chinese can consider an air action each turn from about mid 1942 onwards to increase the number of ground strikes that are possible against the Japanese.
Above all be aware that the Chinese cannot win the war against Japan. It is up to the Chinese to be enough of a pest, however, to make the USA's job of winning the war against Japan much easier. So once China moves to a limited offensive position against Japan, consider the sort of targets that are going to make the USA's job easier. For example, if those air actions are used to (successfully) ground strike Japanese marine units within range of the Chinese bombers, or even ground strike an unprotected Japanese NAV bomber, all the better. Don't focus entirely on the objectives that will help China, also consider the objectives that will help the USA.
(as an aside -- there is a change to the rules in v.8 of the WiFFE rules, not implemented in MWiF, where (a) the nationalist chinese attack weakness is no longer an optional rule, it is a mandatory part of the game and (b) a very nasty rule where if either faction of the Chinese, nationalist or communist, run out of cities then all of their units are *scrapped*, not *removed from the game*. Scrapped units can't ever re-enter the game even if their country is later liberated, and so if China is conquered and then liberated it doesn't ever get any units back. It is therefore essential, if somewhat difficult, for the Allied players to do everything possible to ensure that China isn't conquered. This is one of the primary reasons I have stopped using version 8 of the rules and reverted to version 7).