Using LTM Policies to rewite URL

Because the policies are designed for simple modifications, I don't think you can get that level of functionality. If you want something like a static host rewriting on request, you can do that, but as far as I know, you can't really get generic/dynamic with replacements using LTM policies.

For functionality like that of proxypass iRule, you wouldn't be able to use a policy. For me, I've used a custom form of the proxypass iRule that's a little simpler and more tailored for our environment. I was asking the same question you are to myself, but from my experience it was sadly not possible.