I really feel like it is going to be hard to 'fix' orks for 6th, and I'm really afraid that any 'fixes' will screw up the fluff, or boost heavily used units (lootas, shoota boys) just as much as the struggling ones.
I'm not sure how
GW didn't see something this basic, but:
disallowing consolidating into a second combat
disallowing first turn assaults
disallowing most (with the exception of Zagstrukk) deep strike assaults
disallowing disembarking and assaulting (with assault vehicle exceptions)
combined with random charge ranges, AND free Overwatch (snap shooting)really served to totally bone assault based armies. I can totally understand either random charge ranges, or Overwatch fire, but BOTH?
Mechanically, Overwatch is there to mitigate against the IGO-UGO nature of
40K, so that units don't get assaulted without any opportunity to fire short ranged weapons. That's totally a valid concept, but there's no downside to Overwatch (sure, you hit less, but they are extra free shots). There's no other option for units which don't shoot, have poor shooting, or which would prefer to do something other than shoot. If you had an actual set of charge responses, say:
Overwatch: as listed
Stand your ground: no overwatch, but enemy does not get bonus attacks for charging
Flee! Subtract
d6 from enemy charge range (to represent the difficulty of engaging an enemy which withdraws)
Counter-charge: add
d6 to enemy charge range, but both units count as charging (giving melee-oriented troops a boost)
Then, overwatch might be better, since it would be a choice, not an automatic benefit for shooters.
On top of the overwatch, they added random charge ranges, which ALSO mechanically serve to mitigate an IGO-UGO system (you don't need BOTH). A failed charge is just a way for the game to represent "you didn't get to fight these guys before they got to do something". But now, troops being charged get to shoot at you, and THEN, you might fail the charge and get shot at again!
On top of that, they preserved (or expanded) prohibitions against many types of rapid assaults (out of transports, from board edges, from another combat, from Deep Strike), all of which would be adequately represented by the random charge range mechanic too (or a variation thereof). Maybe charging from the board edge would be
2d6, take the highest (or lowest)?
Instead, all of these assaults are banned, and then, on top of that ban, the random charge range, and the Overwatch rules, mean that, for instance, troops emerging from a board edge might take four 'rounds' of shooting before being able to assault people RIGHT NEAR THEM:
Kommandos appear on board, and cannot assault.
Enemy shoots at them on his turn.
Kommandos declare a charge.
Enemy shoots Overwatch at them.
Kommandos roll poorly on charge range.
Enemy shoots at them on his turn.
Kommandos declare second charge attempt.
Enemy shoots overwatch at them.
Even with minimal charge distances and good rolls, the Kommandos have to weather two 'rounds' of shooting, no matter what.
I just think the mechanics of 6th edition fundamentally nerf assaults in favor of shooting. I can see how scads of special rules might help mitigate that, but they are covering up an underlying problem, in that
GW saw a real problem (assault hopping) and haphazardly applied multiple fixes to a single problem.
Having said all that (

), I hate, hate, hate army-wide
FNP for the orks. There's just nothing in the background to suggest that the average ork shrugs off autocannon rounds occasionally.
I'd like to see:
Dying Blow: In melee, engaged ork models make their full attacks, even if killed in a previous initiative step (though they cannot make a consolidation move on their initiative step).
This would represent orks fighting on even after they were dead, and it would also serve to boost Slugga boys vs. Shoota boys. It would also make
PK Nobs a bit scarier to challenge (as they might kill you no matter what).
Choppa: AP6 (the most common ork weapon goes through the most common Ork armor. Hmmm...)
Big Choppa AP4 (which gives this weapon more reason to be taken)
Power Klaw: given the mass of ork Nobs and Warbosses (even if their S4 is the same as a marine S4), Power Klaws DO NOT go at initiative 1. Maybe -1 intiative, but there's no reason that the massive Power Klaw of an ork has to work exactly like a power fist. This would differentiate Ork Nobs from Marine Sergeants and the like, and make challenging a dedicated ork fighter a slightly worse idea. Maybe Power Klaws go at Initiative 2?
Eliminate the current rules for the Waaagh.It doesn't seem to work particularly welll, nor does it represent any part of the Ork background very well. I don't have a good rule replacement, but it should:
represent orkish eagerness to engage in combat
occur relatively early in the battle (don't most ork fights START with a Waaagh?)
Push the orks forward towards the enemy a meaningful amount
Allow an assault (what's the point otherwise?)
have the drawback of pulling ork units out of position (not grot units), so that a Waaagh might be detrimental to your lootas, for example
Perhaps you could replace a single Waaagh with unit specific Waaagh checks. Every turn, each ork unit could make a mob size check (if desired) and, if successful, could run and assault that turn. This would allow shooty orks to hold a desired position, and it would also serve to boost shoota boys, as well as differentiate Dreads (who are orks, and can Waagh) from Killa Kans (who are grots and cannot). You would have to come up with some way to make Dreads able to check (but that should be easy).
Reintroduce
Mobbing Up. I think this was one of the easiest ways to represent the resilience of orkish morale, and it was easy to do on the tabletop too. The unit that is
'absorbed' is considered destroyed for all rule purposes (Kill Points, Victory Points, First Blood, whatever).
Strength in Numbers. Allow the number of orks to OVERRIDE the leadership value, not replace it. Anything which modifies leadership does NOT modify the number of orks for this purpose.
Kommandos have Tankbusta bombs. Given that they had them in the last rulebook, and the current models STILL HAVE THEM, this was a dumb change.
Ork Walkers are poorly armored, but ramshackle and highly redundant in operation. Give Kans 3 Hull Points, and Dreads 4 Hull Points. It might be easy to shoot stuff off of them, but they take a beating. Boost the Mega Dreads as well. This is already a factor in the Stompa (which has many more hull points than other Super-Heavies, even though its armor is fairly light). I would also boost Buggies if they get a new model which isn't tiny.
Orks used to have a higher Strategy rating just for the purpose of determining who went first (otherwise they had a fairly low strategy rating for determining who choose the scenario, etc). Allow orks to reroll (or force a reroll) on Seizing the initiative, because their inherent battlelust often takes opponents off guard.