Weapon specialization (Basic fantasy)

Trying my hand at an alternate take on weapon specialization for fighters for my Lost realms campaign. 

Fighters at level one can pick a specific weapon to become experienced in. Being experienced in a weapon gives the fighter a +1 to hit. and all rolls of a natural 20 does maximum damage. 

At level 4 a fighter can choose a new weapon to be experienced in, or choose to become specialized in a weapon previously experienced in.  Being specialized in a weapon gives the fighter a +1 to hit and damage, and maximum damage on a natural 19-20.

At level 7 a fighter can choose a new weapon to be experienced in, or choose to become specialized in a weapon previously experienced in.

At level 10 a fighter can choose a new weapon to be experienced in, or choose to become specialized in a weapon previously experienced in. a fighter can also choose to master a weapon previously Specialized in. Having mastery of a weapon means the fighter rolls two dice when rolling to hit and keeps the best of the two rolls and does maximum damage on a natural roll of 19-20.

Experienced: +1 hit, Max dmg of 20

Specialized: +1 hit and dmg, Max dmg on 19-20

Mastery: Best of two rolls to hit, Max dmg on 19-20.