### I would never choose this spell because NPCs generally don't make Charisma checks.

I've been DM for a lot of games, and played in a lot more, and the thing this spell tries to do just doesn't happen. *NPCs are generally trying to persuade/deceive/intimidate against the player's agency, not making charisma checks themselves*. Think about some of the examples you mention in the question. Merchant is haggling over the value of an item: does the merchant roll deception for its value, or does the player roll Insight or Persuasion or Deception or Intimidation? In most scenarios, *it is the players that do the rolling*, because it is the players that are here to play the game. Having the NPC rolling for the Persuasion check can take away form the player's agency:

>Player: I don't believe the shopkeep about where he got this sword.
>
>DM: Well, he rolled a natural 20 in deception, so yes you do.

Having the NPCs making the Charisma checks just doesn't work well with player agency. So to answer your question, "is this a well designed spell?", no it is not. It fails to consider how the game is actually played. It might work as a minor set piece that an NPC might use against the player characters, but NPCs do not themselves make enough charisma checks for this to *ever* be a viable choice of spell for a player character. At best, all this spell does is have a chance it giving people hiccups with no mechanical consequences. It doesn't matter if it is a cantrip or a levelled spell, the design just isn't a choice players would ever make, unless they are *really* into making people have the hiccups. 

As a final note, you mentioned possibly using this spell against other player characters. I would be very careful with this, PVP is best engaged in *when it has been agreed upon beforehand*. Surprise PVP can be not fun and quickly lead to hurt feelings. But when everyone has bought into the possibility of PVP, it can be great.