Although PIF-PAF is a great system that gives advanced agility to interceptor missiles, it is not a must.And we're still waiting for that, unfortunately...
Especially within atmosphere applications, TVC and traditional fin systems are more than adequate for fine manoeuvring. Our dual pulse interceptors all use TVC and fins to manoeuvre.
Things get a bit complicated when you start intercepting in rarified atmosphere and in space.
If you check SM-3 Arrow system; you have “Divert and Attitude Control Systems” in play there (DACS). There are at least 10 nozzles as pictured below that are activated in space, as and when needed, to give fine manoeuvring capability to this hit to kill missile.
Each of the 10 or so nozzles have individual throttle capability to adjust the amount of thrust applied in any one direction. This gives very precise manoeuvring.
If you investigate the video of the PIF-PAF system operation in PAC-3 missile in my above post, you will find that they utilise multiple explosive solid propellant rocket motors that activate as and when needed.
We have in the past tested our own PIF-PAF like systems under laboratory conditions. But we don’t know the type of exo atmospheric interceptor we will use.
We have seen SM-3 system intercepting Iranian missiles. We may use a similar system.
At the end of the day it will have to be the most economically and technically viable system to suit our needs and respond to the threat level we have around us. I would say wait until Siper Block 3 comes out. The finalised configuration of this block will be for high-altitude ballistic missile interception with the longest range in the family. (Presumably in excess of 200km)