The "perfect" knife is the relativley unexpensive one that you carry with you...
The three hundred quid one crafted from finest unobtanium with the vanishingly rare exotic hardwood handle that's left at home cos it's "too nice" to use is about as much use as an ashtray on a motorbike
It's amazing that prehistoric man managed to evolve modern levels of sophistication without owning any one particular type of knife, perhaps they were just far more adaptable than us...
On to the "handedness" of the sheath, why not just make a certain amount (about 13-15% if
THESE figures are anything to go by) of the sheaths for southpaws and offer a factory exchange policy on new sheaths so if someone buys a knife they can exchange sheath for the right one?
If they buy a secondhand knife then they will have to buy it instead cos otherwise the factory ends up with loads of secondhand sheaths.
That was you don't have an ambedexterous sheath that looks like a right dogs dinner.
Also the knife should come from the factory with a few scratches on it to stop people poncing around with them
, a bit like Land Rovers should have a few factory installed dents and dings so people who buy em don't just do it to pose in Tesco's carpark and never take em offroad.