I agree with
everything you've said, except this. 10 of these
should be able to destroy 2 things, depending on what he's targetting.
The issue with an Ork Gun line is that your range of the
KMKs are only 36inches, so you're forced to typically bring your gun line quite far forward for it to be effective, which isn't what you'd want to do with a gunline.
A few things:
1. The
ADL, which Fcadmartori suggested, is a must
IMO. Give it the Quad Gun and your grots will have something to use. 19 grots are better than 20, as you don't need that extra Runtherd, saving you points.
2. Lobbas are 48 inch range, barrange, Strength 5 AP5, and 12 points cheaper than the
KMKs. I would suggest taking 5 of these, then 5
KMKs. This will free up a good chunk of points.
3. As Fcadmartori advised, put Ammo runts on all your artillery. Never don't do it.
3. Lootas are awesome. Again 48inch range. A full squad of 15 means means your getting your money's worth, filling out the 3rd heavy support slot. Best source of Strength 7 in most codexes, and really cheap for their points. Behind the
ADL, they can go to ground and aim at fliers, snap shooting isn't a major issue for orks as our
BS is so poor anyway.
4. Get a Painboy. If you have 20 foot sloggin boys, they won't survive long out in the open.
FnP is awesome for them, tho I can understand wanting to use the Weirdboy.
5. Put Rokkits on your Boys. Rokkits are awesome. Shootas are pants.
6. As a distraction unit, either Tankbusters (in a trukk), Meganobz (in a trukk), or a Deffkopta Deffstar unit are really useful, as they are able to destroy stuff which tries to hide out of range or out of sight of your gun line. The later 2 are useful as your army DOES need a combat piviot, incase there are any units which choose to close the cap between too fast for you to shoot down.
7. Ork gun lines might struggle at 1000pts, but i would definately take 15 lootas over 5
KMKs at this level.
KMK are really nice, but Lootas just have that range.
Extra point: for true dakkaness, buy the Fortress of Redemption

You get some seriously nasty weapons on that thing...