The position as goddess of magic seems to be really popular 😉
Would also be a nice goal for a sorcerer Tav. But Lolth is a pretty tough competitor, I don' t think this would end well...
Let's face it... Mystra is kinda cringe. She has no personality at all and she sucks at being the goddess of magic (died 3-4 times already?).
Now Lolth would be a much better fit for a lot of reasons. She has ambition, she has talent, she obviously knows how to stand on her own two feet, and has a talent for intrigue and subtlety, she has a certain mystique, not to mention the fact that magic works through the Weave and Lolth is a spider. What do spiders do best? They weave. It's thematically fitting.
Also, Lolth would still be forced to provide magic for everyone equally, the same way Mystra was forced to do so because Ao made her do it, so this wouldn't ruin magic for anyone (except for, ironically, elves, who hate Lolth enough to give up on magic lmao), but it would make the setting a lot more fun and unsettling and I can just totally see Lolth instantenously starting to plot against Ao, but unlike the Dead Three, she would actually be smart about it.