this sounds like a good flaw, and I think our Mr. Greenhilt may have taken it as well.

how about these changes, choose a melee or ranged weapon, whenever you use a weapon of that type with a different classification then the one you chose (light/1hand/2hand) you take a -1 penalty with that weapon, also whenever you use a weapon that deals a different damage type (slashing/piercing/bludgeoning) you take a -1 penalty, these penalties stack when you are using a weapon that is nothing like your chosen weapon.

so Longsword to Greatsword is -1 and longsword to club is -1, but longsword to spiked chain is -2