how should their abilities work? cause in the board game their spells are random to ur roll of da dice.

The tabletop is not a good representation of how anything ought to work. Probably the 40k RPGs (Deathwatch, Dark Heresy, Rogue Trader) are better. Anyway, the bottom line with weirdboyz is that there's a random element to it. That's orks, right? They can easily add in a moderate random factor, but I think they would be unwise to make their abilities too random. At the end of the day, nobody wants to lose or win their fights largely by what numbers the computer rolled for them, and whether their head exploded instantly at the start of the fight or not.

They could just add some sort of meter that dictates how much "Waaaugh" your abilities have.

For example say if you wanted to X ability, it generates 15 Waaaugh on your Waaaugh meter (lets say that the waaaugh limit is 100)

As your W increases your abilities become more powerful, they also become more hazardous. At 100 your abilities hurt you, the only way to keep it down is to, say stop using abilities or some other such mechanic.

like that idea.

So basically what Bright Wizards/Sorcerors had in WAR?

They could have that system, but instead of just having defences lowering/self damage some abilities could have "alternate" outcomes, with lotsa W, the alternate outcome would come more often.
Lets take some abilities from the Tabletop and see what we can come up with.

Zzap-Anti vehicle ability, with its incredibly high damage I cant really see backfire damage as sustainable (without severly damaging the weirboy) so maybe a 3 second stun?

Frazzle- Pretty good anti infantry ability, eadbanger maybe?

Warpath- gets orks multiple attacks in combat, alternate outcome could be debuff all allies in area?

Ere we go- instead of going to a predetermined destination, why doesn't the AO become a random destination (within range?)

Waaaugh- Could see this as long cooldown move, AO could just be no effect at all?

Off the idea of the waaagh meter what if using a certain combination of spells allowed you to go beyond the 100 (optional for the risktakers) but if it is your spells are alot more powerful but there is also a % chance of you causing your own and all other orks in your parties heads to explode. (that was a risk of the waaagh correct?)

While the previously mentioned mechanic is good, it's actually quite the opposite of what fluffy weirdboyz do. They are said to need to use spells to discharge the waaagh!! energy that builds up, less suffer becoming a 'eadbanger(the weird boy is filled with so much Waaagh!! energy his head, and those of any unfortunate orkz near him, explodes.)

So perhaps instead of it growing with spell use, you can have a bar that fills up passively in combat, and you must use spells to keep the meter from getting to high or cause yourself to explode (for gameplay reasons you can just cause an explosion that hurts allies or such.) Also, the bar would increase faster if there are more orkz fighting near you, within reason of course.

In fact, you could work in some sort of risk/reward mechanic, the higher the bar, the more potent your spells become, but you run the risk of 'eadbangin the higher you get.

Also, hello everyone! nice to meet you!