There is a formula to the damage/abilities thing. You can make the following changes without affecting balance.
1.Change 19-20 x2 crits to 20/x3 crits or vice versa.
2.Change trip for +2 to disarm or vice versa.
3.Drop the damage by one step d10->d8 or 2d4 or d8->d6 and improve the crit from 19-20 to 18-20 or x3 to x4.
4.Change the damage type (bludgeoning/slashing/piercing) to any other type.
So, suppose you want to make a crow's beak weapon. Its piercing with truly dangerous crits. Since it dosn't have either trip or disarm, lets start with a glaive. Let's change the damage type from slashing to piercing. Then lets drop the damage to a d8 and boost the crits to 20/x4. So this gives a balanced weapon.
Stats: d8 damage, piercing, reach, 20/x4 crit.