Alright well, here's some issues I have.
The air thing was already addressed. It spread virally after I first did it I suppose. In that game though I also invented another tactic: barracks funneling. Zombies won't automatically target the barracks, which for their price are effective walls, so I was able to funnel a lot of zombies through a choke, being able to decimate them. Even if they target them directly, they're so buff they allow me to mow zombies down.
In the cliffs of Italy, above the zombie entrance cave, I was also able to drop snipers, which are able to be very effective if the zombie player can't get both air and ranged out simultaneously. I haven't tried France though it may be possible there.
One of the air units has the sounds of the Raven. The Bomber. I'd recommend changing its model to be a Raven seeing as how two units already use the Viking model, and the Raven unit was a spellcaster so it'd also fit with its SC2 counterpart.
I'd recommend a new loading screen. The image is stretched out far too much and it looks very grainy.
For the water, there is no reason to lower the terrain beneath. Up the alpha channel of the water you're using, it'll make it less opaque so there's no worries about seeing the ground underneath.
Vespene income also slows to practically a standstill once your capital falls, which makes it incredibly difficult for important nations like Italy or France. This problem is mitigated to an extent with leavers; their vespene income gets transferred to you, but it's still a problem. If their capitals die then your vespene income is also gone. 0 capitals in the game = 0 gas income for all humans. And games can come out that way.
There is also no "newbie" guide if you will. New players have basically no direction about what to do and what they need to pay attention to. I frequently encounter players with this issue and it's not really their fault.
Captains are useless, and feel incredibly vestigial. Especially the melee ones. I really do not care if they die.
I was also able to drop SCVs onto the cliffs of the zombie caves where I could build, in addition to all other cavern issues listed before.
Remember that SC2 armor works differently from WC3 armor, so you can't just cut and paste attack values. For instance, the Gatling Gunner's damage is cut in half because of a single armor point on zombies. It's not just a % reduction.
Sniper towers cost a ton of gas.
Zombies can mass up their entrance impossibly.
I'd also suggest some sort of Broodling explosion for when zombie buildings die.
It's also very hard to infiltrate a smart zombie; he can place a ton of Spitters behind the first cavern wall which we aren't able to gain vision of and kill them while he has melee zombies tank our advance. Zombies have a humongous advantage if they use vision correctly with their cavern cliffs.
Also, there's still all the UI problems, obviously, such as the wireframes, the armor potraits, the death animations, etc.
Lastly, there is no reason to cling to the WC3 version just because. This is a time to reinvent and refine. Don't hold the old map up on some pedestal as if it was infallible.