Nyssa, for example, is just fine.
Nah. I'm tired of "Ra's al Ghul and His Whacky Kids." He was a cool villain. Everything that's been related to him has been problematic, IMO.
The new Ventriloquist is no more or less ridiculous than the original one.
One could argue that that's not saying much.
Then there's Talia, Poison Ivy, and Catwoman, all of whom are respectable enough. Harley's not too bad, either.
See, I disagree with your basic premise here.
Talia was
never a good villain. She's the perfect example of comic books getting everything
wrong when trying to be PC. "Oh, look, here's this strong female character! Never mind that she's stereotypically torn between love for two men, and that those men are her only motivations for doing anything, ever." Yeah, that's enlightened.
Poison Ivy? She's a one-gimmick villain. She
can be cool, but she's misused as often as she's used right. And certainly she wouldn't transition well to the more realistic tone of the movies.
Catwoman's not a villain. She's a rival, or a secondary villain at best. She's neither as interesting nor as menacing as any of Batman's "first tier" villains. And she, too, falls back too often on the "female villain falls for the main hero" cliche.
Harley's a sidekick. She doesn't work without the Joker, and frankly, she's a little too silly for my tastes. She's like the
old Joker--goofy without sufficient menace. Plus, again, she's 100% defined by another character; she only does what she does, and is what she is, due to her infatuation with "Mr. J."
Bats' male villains are often just as ridiculous as his female ones - to every Orca there's a Great White, for everyone like the Joker there's someone like Tweedledee and Tweedledum.
Oh, there are
plenty of goofy male Batman villains. But there aren't any cool/menacing/dangerous female villains to make up for the goofy females, while there
are plenty of cool/menacing/dangerous male villains.