Definitely some flaws in your work, and Alerian has expounded on some basic principles of things to change. I play mechanized orks. Battlewagon orks if you like. I don't do too shabbily with them at all, and I wanted to add a few things.
1. THe
KFF wagon isn't just invaluable - he provides a 50% more life expectancy. It is possible to deploy your battlewagons and move them in a trident formation \|/ that literally presents front armor across the board, and having a 4+ cover save...having mobile cover that you take across the board with you wherever you go is critical to sustaining your livelihood.
2. The most important moment of the game....the most important part of every game you play as a mechanized ork player is your initial charge. The entire game up until this point is nothing more than clever maneuvering and preparation for you assaulting. Consider Ghazghkull Thraka and the force multipliers he brings to your army. He extends your charge radius an automatic 6", and is single-handedly very likely the most potent close-combat model in the entire
40k universe. Seven STR10 attacks on the charge with a 2++, 4 wounds, and
EW. I consistently send him into combat alone. He annihilates everything. Honor guards, nob bikers, Blood Crushers...and on top of that, he makes your entire army fearless for a full player turn, meaning that you don't need to worry about running or breaking in shooting/assault.
3. Wise advice on the killa-kannons. Keep in mind that they are an underpowered overcosted mimicry of the battle cannon. Worse, you don't get
PotMS or anything that lets you shoot and move, so your two choices are such:
-Move 0" or 6" and fire the killa-kannon, thereby wasting the battlewagon's carrying capacity and ability to get you up to the front lines quickly
-Move 12" to use the carrying capacity and don't fire the killa-kannon.
Either way, you're wasting something. The only configuration that makes the slightest sense at all would be a killa-kannon with 12 Lootas inside as a mechanized bunker on your back lines. But even that is wasteful; I'd rather have the extra 3 Lootas than a killa-kannon.
4. I've grown strangely attached to my gretchin. A unit of 10 gretchin with a single runt herder is a 40 point scoring unit. In capture and control missions, they hold your rear objective while the other 1960 points charges forward, which is a far cry better than leaving 200+ points in the back to hold your objective. In seize ground, they can be an easy objective holder while you go somewhere else. Ponder that.
5. This is a mechanized world we live in, and there's a few pieces of wargear for my battlewagons that I've found pretty much mandatory: Boarding planks, grabbin' klaws, big shoota. Your deffrollas aren't always going to hit their target. When they do, they're not always going to explode it and let you continue on. Boarding planks let your embarked powerklaw take some swings at it. And in case that fails, a grabbin' klaw lets you grab it during your opponent's next moving phase so that you'll auto-hit next turn. The big shoota is so that you can survive a weapon destroyed result. Keep in mind that if you have a
KFF in your list, you also have mek's tools to try repairing battlewagons, and a grot oiler is a reroll.
6. Meganobs. Eww. Exactly what can meganobs do that regular nobs can't do better? The problem arises when you think of where you *need* meganobs. Or better, where a unit of boyz isn't enough. Throwing a unit of boyz at a unit of
MEQs is easy - you have overwhelmingly more attacks, you're going to win. Throwing that same unit of boyz at a unit of terminators with lightning claws....now you're going to lose.
TEQs are problematic. So are
MCs - all those boys need 6+ to wound, and against some tyranid
MCs (like hive tyrants and swarm lords) there are other nasty things that will cause double wounds, or
ID. Force weapons, nemesis weapons, units with flamers....all of these are bad news for boys.
The problem is this: Your alternative answer for the things boyz are ill-equipped to handle is a unit of meganobs, who are equally poorly equipped to handle the situation. Against a unit of
TEQs, you're going last, and you have no invulnerable saves against all those lightning claws. God forbid they have thunderhammers - you're going to lose a bunch of meganobs while they shrug off 66% of your powerklaw hits with their stormshields. Against
MCs....you get no saves against them, and while you'll probably win, you'll take casualties. You'll do better against flamers than boys will, unless those are being toted by ORKS, in which case you're going to get hit by a big unit of power-weapon toting boys who will rip you a new one before you get to even think of hitting back. Your 8 meganobs against my 15 burna boys. Your 320 points against my 225 points. 45 attacks at I3 says that I get 12 wounds, and you lose 6 meganobs. Your two strike back and kill 2-3 burna boys. I'll take it.
My point is that a regular nob squad can do everything a meganob squad can do, and do it better. Take a unit of 8 nobs instead. Equip them all uniquely. Give them cybork body and a painboy, so they have a 5++/4+
FNP. Now, you have a 5++ against
ID, which the meganobs don't, and if you take two wounds...or four wounds...or 6 wounds....you still don't lose a model.
There's more, but I'm out of time this morning.
Warboss Lemmy's Speed Freaks: 1730pts painted
+ 
Skullbearers: 750pts painted
