A thought on characters learning weapons outside of what their class allows.
As you know, some classes are limited due to their calling, (such as clerics only using bludgeoning weapons). These characters cannot use new weapons in that it goes against their religion. But what if they worship a god of hunting? Maybe they want to learn to use a bow?
Some classes are limited due to logic, (such as thieves using smaller weapons that are functional in small spaces). But, what if a thief finds a special warhammer that is good at knocking down doors and he wants to use it?
Some classe are limited due to complete lack of training, (like a magician with their lone dagger). But, what if that magician had a military background and wanted to learn to use a sword?
I propose a simple answer to these questions: The ability to learn weapon proficiency. A requirement for this “skill” is to know the Fighter skill. After all, you have to know how to fight to be able to learn the intricacies of specific weapons. (So, the cleric and thief above can just learn weapons out of the gate, but the wizard would have to learn the Fighter skill first.)
When using the weapon in a conflict, it is considered an improvised weapon (no penalty due to being unarmed, but no bonus from the weapon’s abilities). But then the character could Beginner’s Luck whatever the specific weapon is instead of using his Fighter skill. (Halving Health to learn the skills Bow, Warhammer or Sword in the above examples.) Once the character learns the skill, he can use that specific weapon with full benefits. (The wizard could use a sword, but not a two-handed sword or rapier, for example.)
You could also learn the skill via the Mentor skill as normal, as long as the teacher is proficient with the weapon.