The more I think about Expertise and Bounded Accuracy, the more I want to limit Expertise. I do, however, think it is something that should be available, if in limited amounts. The Rogue and the Bard each get Expertise for only two skills at a time, and this feat should follow that same maximum.
TRAINED
You may take this feat more than once.
You gain any combination of the following benefits, adding up to 10 points:
5 points: Increase one ability score by 1, to a maximum of 20.
4 points: Learn a cantrip(1), or gain proficiency in light armor, medium armor(2) and shields, or heavy armor(3).
3 points: Gain proficiency in simple weapons, martial weapons(4), or shields.
2 points: Gain proficiency in a skill(5).
1 point: Gain proficiency in a tool(6), language, or weapon.
(1)If you learn a cantrip, you may choose Wisdom, Intelligence, or Charisma as the spellcasting ability modifier for that cantrip.
(2)You must be proficient in simple weapons before gaining proficiency in martial weapons.
(3)You must be proficient in light armor before gaining proficiency in medium armor.
(4)You must be proficient in medium armor before gaining proficiency in heavy armor.
(5)(6)Expertise: If you choose a skill or tool that you are already proficient in, then your proficiency bonus is doubled for any ability check you make that uses that skill or tool. You may gain both proficiency and expertise in a skill or tool through one use of this feat. You may gain expertise in at most two skills or tools each time you select this feat.
(6)At the DM's discretion, proficiency for a particularly useful tool may cost 2 points rather than 1 point.