If I had an hour I couldn’t explain all the things wrong with this.
But please take away from this that you never, ever want to be on the floor with a stronger attacker. Ever. At all. Bad news.
Let me add to this and say that yes, it’s a very bad idea. I assisted in a rape prevention class once, which doesn’t make me an expert by any means, but I did have about 30 women use me as a test dummy. Basically you want to do whatever you can to take him out of the fight immediately.
Ideally you want to drive your thumb as far into his eye as possible. Which is hard, because you’re a good person and your natural instinct is not to permanently injure another human being.
If he’s holding both wrists, you can certainly try to knee him in the groin, but there is the risk of missing. Do not hit the “front.” Come up from below as HARD as you can, as fast as you can, with your forearm. You can’t miss with your forearm. Something like a kick might give him the opportunity to twist away, unless you practice a ton.
If you can get one hand free, the eye is always best. If you can draw blood on his face, you might scare him off, because now there is proof of his attack, and his skin cells are under your fingernails.