Welcome to the JavaRanch, Alexandre!
No, it is not possible. JSF tags are processed by the FacesServlet. In order for any other servlet to replace the FacesServlet, that servlet would also have to replicate the JSF internal functionality provided by the FacesServlet.
You can - and I not infrequently do - put a stock HTML FORM on a JSF page that posts to a stock servlet or
JSP, but of course, it acts just like any other HTML form. Meaning no JSF-supplied validation, no auto-population of backing bean variables, no auto-initialization of form control values, and so forth.
JSF provides managed beans instead of servlets because most HTML forms processing follows certain basic rules. Instead of making you replicate those processes on a page-by-page basis, JSF provided a Model/View/Controller framework where the FacesServlet and tag functions supply the Controller functionality so that you can define the View in an abstract View Template Language and your UI Model objects can be implemented in POJO code rather than having to code specifically for a given environment (such as the web) or framework (such as
Struts).
The whole point of JSF, in fact, is to minimize work and reduce maintenance costs without requiring complexity or arcane code.