A number of character classes features that allow them to double their proficiency bonus when using selected skill proficiencies. An example is the Bard's:
[C]hoose two of your skill proficiencies. Your proficiency bonus is doubled for any ability check you make that uses either of the chosen proficiencies.
As far as I can tell, there seems to be two ways to go about this:
- Let the character select from among their existing skill proficiencies. Examples: Expertise (Rogue), Expertise (Bard), Canny (Ranger, TCoE optional feature).
- Let the character select proficiency from a list of a specific skills and immediately grant the ability to double their proficiency bonus with the selected skill. Examples: Blessings of Knowledge (Cleric Knowledge domain), Survivalist (Rogue Scout).
The question is whether there is any precedent for requiring the character to choose from a list of specific skills where the character would not automatically get proficiency if they don't already have it, and would therefore not gain any benefit if they did not have proficiency in any skill in the list.
Not relevant to the answer, but my motivation has to do with ideas for homebrew classes and features. In particular, I am put off by the way the Scout's Survivalist class feature works. If a player intended to play a Scout, the optimizing choice is to not take a background with Nature and/or Survival, because at 3rd level you will get both skills and expertise (https://rpg.stackexchange.com/a/125024/25766). If you already have the skill, you still get expertise, but it's a wasted skill proficiency slot.
What I would like to do is create a class feature that either:
- Grants proficiency in a skill if the character doesn't have it, or grant expertise if the character already does have it.
- Grants expertise if the character has the skill, but no new proficiency if they don't.
Obviously, homebrew is homebrew, but I'd like to know whether anything published does something similar.