While i can see the damage bonus, i think they want to stay away from modifiers (Made some of my suggestions with similar ideas, but i get the base idea is that it is meant to make it as stream lined as possible with using as little math as possible).Page 45
Under Grip, this makes no sense in some context. Some weapons you just can't grip in more than one hand. Short Swords, Hand Axes, Scimitar, among others, they simply don't have the length of hilt or handle to make it viable in combat.
The other thing is that if you can put both hands on it, you get better control and able to exert more force. I would suggest being able to add a total of +1 to +2 to damage.
As for grip, i can see what they what they are going for. Some of the weapons have longer handles that what it might appere (Like some handaxes). But that said, i do agree on swords it might not be viable.