Yes, all things are possible. You'll also have to keep state and track rates. Otherwise a very low error rate could down all of your backend hosts. But you're

Yes, all things are possible. You'll also have to keep state and track rates. Otherwise a very low error rate could down all of your backend hosts. But you're now running a stateful l7 application proxy. That's waaaaaay more expensive than a tcp proxy with asynchronous checks.