I don't think you will have any option but to take the JNCIS-ENT along with your JNCIS-QF exam. I understand there are two reasons for this.
1-The JNCIS-QF only covers the switching "up features" of the Q-fabric line. So there is a requirement to have all the normal specialist level switching covered by the pre-requisite exam.
2-There are some significant differences in layer 2 operations between the SP hardware and the EX hardware. So while there is some overlap between your JNCIS-SP and JNCIS-ENT there are also items uniquely covered in each track.