Skyscraper
Adventurer
To the original topic: I would allow spellcasting to be automatically subtle, where the spell is useful only if it is subtly cast. Thaumaturgy and charm person are very good examples of this. Imagine Gandalf in Bilbo's home, moving away to case Thaumaturgy before looming over Bilbo for a dramatic influence. What a letdown!
Honestly, allowing spells to influence social interactions is simply cool. It's rare that the situation allows them to work, if on top of that you need a phone booth to cast the spell in, before moving out and being allowed to benefit from the spell's effect, you're simply confining spells such as Thaumaturgy to non-existence, or just about.
This won't break your game. It will make it better.
Honestly, allowing spells to influence social interactions is simply cool. It's rare that the situation allows them to work, if on top of that you need a phone booth to cast the spell in, before moving out and being allowed to benefit from the spell's effect, you're simply confining spells such as Thaumaturgy to non-existence, or just about.
This won't break your game. It will make it better.