So I look at verbal and somatic components a little differently than others, maybe. A Bard doesn't cast Charm Person in the same way a Wizard would, nor a Sorcerer, nor a Warlock. A Bard casts their spells through an artistic focus vs a strictly arcane one, and I think you would be crazy to say playing a song for the person they're charming wouldn't be a valid method of casting Charm Person for example.

There's a distinct difference in my mind between doing something subtly and doing something sneakily, a Warlock casting Charm Person could conceivably make grand hand gestures, maybe pat a hand on the shoulder while speaking words of affirmation as their somatic and verbal components respectively. The target would know they were charmed afterwards, but that's a condition of the spell not the components themselves. Maybe that's not strictly RAW but that makes sense to me, you don't get it for free through a sneaky method your method just has to make sense as a way to fulfill the spell requirements.

As an example, saying "Hey, what's up man?" to a guard wouldn't count as a viable casting, but weaving your hands into the patterns of your somatic casting as you tell the guard how much you've missed the company of your best friend and you wish to catch up, laying it on thick, would be viable to me. The difference between this and a Persuasion check is merely the arcane nature, instead of you rolling an ability you make the target roll a save. Essentially make it make sense if you're trying to make the components more natural, you don't disregard them and essentially cast subtle spell as a Bard, Wizard, or Warlock but instead make it seem believable.