Undercrypt, I’m stealing that language immediately. That’s very helpful.
EDIT: Actually, I’m abandoning the idea of different “types” of proficiencies entirely. Instead I’m going to use the idea of different “lists” of proficiencies. You choose from different “buckets” at different times. That is actually more intuitive and closer to the underlying mechanic.
Proficiencies represent particular areas of expertise that your character has developed due to his background, homeland, and training. Each class has a class list of proficiencies, representing training that is particularly useful to the particular profession. In addition, there is a general list of proficiencies, which represent trade skills and knowledge that is widely available to all. Characters will learn proficiencies from both lists over time.
All characters begin with the Adventuring proficiency as well as one proficiency chosen from their class list and one proficiency chosen from the general list…
Note that some proficiencies appear on both the general list and the class lists. For example, Performance appears on both the general list and the Bard class list. This is because Performance is both a common trade skill (general list) and training that is useful to bards (class list).