Delay privilege separation in openSSH

Question

This question is about delaying the privilege separation in openSSH.

This is what I have learned from: Privilege Separated OpenSSH

Monitor process spawns unprivileged process for network processing (key exchange and authentication) and if user is authenticated, monitor spawns user privilege process after which pty will be allocated and user specific shell is spawned.

In my case, I need to spawn a shell (custom script) which first enters into a particular namespace and then call the script to spawn the shell. Since at this stage, user privilege process is spawning custom script, it is not able to enter into a particular namespace.

What I have seen from code that following lines of code in dropping the privilege (in privsep_postauth) to user.

-
668     -
669     /* Demote the private keys to public keys. */   -
670     demote_sensitive_data();    -
671     -
672     reseed_prngs(); -
673     -
674     /* Drop privileges */   -
675     do_setusercontext(authctxt->pw);

Can you guys guide me whether is it safe to do so and also how we can delay this privilege separation until shell is spawned. ?