Although not lightyears apart, there still are a few steps between using a NOTAMed signal to fly something unpublished or forbidden and pulling out the crosshairs visible on the STBY ATT. Come on.
The OP narrative starts with having the FMGS setup for the NPA, hence the PFD indications as well as APCH mode of FD will be slaved to that primary means.
Sometimes a tech question from an eager and technically curious colleague is just that.
Nevertheless, the good advice needs to be respected. Do not fantasize beyond the published way of doing things, the techniques and procedures have been crafted for a reason. 👍