I'll do my best to start with the 1500 point army.
HQ - Warboss, Mega Armor, Cybork - 110
This is a bad option simply because it has nothing to group with that won't be hindered by Slow and Purposeful. I'd suggest losing the Mega Armour, or finding some transport for it (Meganobz in a Battlewagon for instance). Also, this is an infantry army, a
KFF Mek is always a good decision.
Elite - Tankbustas - 155
While Tankbustas are considered a bad unit in general, I'm beginning to think that they're actually viable, but only in low point (~750) games, but become obsolete in higher games (and larger tables) in favor of almost anything else. Tankbustas have to move and shoot at any visible vehicles, whether or not they can actually reach them, meaning they can't ever run, and can be a very frustrating unit to play with in a field where vehicles are prominent (I.E., anything higher than 750).
Elite - Lootas x10, Rokkit Mek
Elite - Lootas x10, Rokkit Mek
I'm generally open minded, but I don't see the benefit in upgrading Lootas to Meks if they're not in base contact with any armor, and more importantly, giving them a worse gun. I'd agree with fielding Meks in a Loota squad if they were positioned RIGHT NEXT to (or inside) a Battlewagon Gunboat, ready to repair that bad boy in case of any damage, but in an all-infantry army, they're just not a Loota, and that's unwise. Additionally, I'd suggest rounding those units out to full 15 man units.
Troops - 20 Shoota Boyz, Nob w/PK, BP - 160
Troops - 20 Shoota Boyz, Nob w/PK, BP - 160
Troops - 20 Shoota Boyz, Nob w/PK, BP - 160
Troops - 20 Shoota Boyz, Nob w/PK, BP - 160
Troops - 20 Shoota Boyz, Nob w/PK, BP - 160
Orks exist in two states: 12 Sluggas in a Trukk, 30 Shootas on foot. That's the formula, it's best not to tamper with it. There is the third option, 20 boyz in a Battlewagon, but I detest that formula, personally. I would drop the number of units to fill out the units into 30 man mobz. And again, with so many models, consider a
KFF Mek.
Fast - Stormboyz, Nob w/PK, BP - 124
Nothing wrong here, Stormboyz when used right are pretty good. However, your army (with the exception of Lootas and Tankbustas) is lacking some real punch when it comes to anti-armor, and this is where I detail the virtues of the "Buzzsaw Deffkopta" which can assault stationary armor 54" away on turn 1 with Power Klaws. That's what I call a "fast attack."