SUCCESS ENGINEERING
Red level
If that is your situation, you should develop the hardest and longest ‘4 in a row’. That means categorising severity, probability and level of detection from 1 to 10. Red level also means you can develop all the tools which are in green, yellow or red from the tool table in step three.
Unfortunately, you will probably need to invest a significant part of your budget in the implementation of ‘4 in a row’. But there is a reason, probably the criticality of your SC, which requires from that effort. But there is also good news: you can fully obtain the benefits of ‘4 in a row’.

Notional example of a 1-to-10 severity classification in a FMEA.

Notional example of a 1-to-10 probability classification for a natural disaster in a FMEA

Notional example of a 1-to-10 detection classification for a natural disaster in a FMEA