I was thinking of constantly updating scoreboard values based on a player's Numismatic balance and possibly vice versa. These scoreboard values can be used for e.g. server-wide leaderboards, custom advancements, and more.

For example, the following commands are effectively the same and should require the same permission level, yet the second is more performant:

1. data get entity @s cardinal_components.numismatic-overhaul:currency.Value
2. numismatic balance @s get

Therefore, the minimum required permission level for numismatic balance get (and ideally set as well) should be lowered to 2 instead of the current 4. This can be done by changing the 4 to a 2 in the following line:
https://github.com/gliscowo/numismatic-overhaul/blob/866f30c3ab83e190c71c9039e824c07eb8c3dd43/src/main/java/com/glisco/numismaticoverhaul/NumismaticCommand.java#L23

Permission levels, as summarized from the Minecraft Wiki:

• 1 -- Bypass spawn protection
• 2 -- Use commands that affect the world. Examples: /data, /xp, /scoreboard, /give
• 3 -- Use commands that are meant for multiplayer management. Examples: /ban, /kick, /op
• 4 -- Use commands that are meant for server management. Examples: /stop, /reload, /datapack, /save

Added in 0.1.6, when it gets released in a few minutes