nPath and HTTP header manipulation

Greetings

Is it possible to use a Direct Server Return (nPath) and at the same time have an ability to manipulate with HTTP header fields in HTTP requests (for example, use iRules for filtering requests by URI)?

Accordingly to documentation, it is required to use FastL4 profile in case of nPath topology. With FastL4 it will be impossible to do something with HTTP (L7) headers. At the same time as far as I understood LTM profiles are iRules itself. So, is there some way to customize FastL4 profile/iRule and make HTTP headers visible or customize HTTP profile/iRule to make bidirectional traffic unnecessary for correct operation?

Thanks