Well they could always say if they go mysterio and he has holo tech and maybe some mind control type gasses. That he doesn't know folks personally but the mix of tech and gasses the victim sees what's in there mind.
Not all villains need to be personally connected to cause pain and misery to pete. Again the only ones for that should be the osborns, brock, conners, and miles warren. Those are the only ones in my book that should have connection to pete and or over series learn his identity. The rest should not.
But I kinda of want people to define their terms, when they say want Mysterio to be unsympathetic, do they mean he should be an unpleasant jerk or a real monster? I think one of those things is more compelling then the others, a monster is about as far as you can go from a sympathetic villain and a monstrous villain can be a high stakes one, if they win, there will grave consequences. Having a really nasty villain, gives someone to really root against, rather then just passively rooting against a villain because he happens to be the villain of the story, but doesn't do anything really bad. Mysterio threatening people's lives makes for bigger stakes then Mysterio just robbing banks.
I don't think Mysterio needs something over the top like mind control glasses to torment Spider-Man, if Spider-Man still a rookie, it would easy for Mysterio to torment him. Imagine if Myterio murdered an important offical right in front of Spidey and that was the first person Spidey failed to save since Uncle Ben and Mysterio uses his illusions to torment Spidey over his failures. Joker is a personal foe for Batman, despite the fact Joker doesn't know who he is or have a past connection to him.
Mysterio seems to be written a couple of different of different ways: generic criminal, over the top campy villain and sadistic mind breaker, I think I like the last one the best. Mysterio can be campy and hammy, but that may just be his exterior, underneath that he is a really cruel individual and the outward silliness can give way to a more monstrous character at times.
Mysterio being a more monstrous foe makes sense, unlike other Spider villains, he was not a victim of a accident, he chose to be Mysterio and his perchance for mind games and psychological warfare just naturally make him unsympathetic, I don't think he has been sympathetic in the comics. I think that might the best direction to go with him.