Yes, I've suggested that certain spells should be possible to cast during dialogue. Nettie is a good example of where the encounter probably should be possible to do with charm person. Of course, if the target resists the spell, the outcome should be bad. Right now I'm with you, I feel like I should hit quicksave all the time just in case I end up in a dialogue where I would have wanted to use charm person.
I'm not even sure if advantage works currently in dialogue dice rolls. You can mouseover the target number to see modifers, but it should be made crystal clear whether you have advantage as well. This is early access, so possibly charm spells just don't work fully quite yet.
