..I am also eager to know.
I please allow me to discuss a few points:

1-But I have the idea that API 579 ( lets talk about edition 2016 ..they are some new things there !!) in its level 1 and 2 does not consider buckling which have law allowable, a very thin local section could be a sort of hinge.

2-There is also another standard which recognizes API 579 , namely ASME B31G (Manual for Determining the Remaining Strength of Corroded Pipelines ) check also there.

3-I suggest to have a look in ASPEN site (by googlinaug) and find a document (title: The Structural Integrity Of Oil And Gas Transmission Pipelines) of Phil Hopkins an authority in this field , there is also an extensive literature there which could give you a lead ?

4-I suggest also to minimize FCA (future corrosion allowance) so you will get a large thickness and have t_min > 2.5 mm and you will be ok. This can be achieved by a proper working cathodic protection/ coating ??

5-Check also if original code design of your pipeline or Company policy/ DEP, or similar prescribe a Minimum thickness ??
Having a very thin wall , even if it is ok, means that you have to replace the line or a portion of this line..on the short term.
A calculation is not the whole engineering, in your decision you have also to be supported by Maintenance, Management and they are also legal and safety issue..so no unnecessary risks.

6-I believe also that you have used part 4 or 5 of API 579 ( local or large corroded areas) but you might also have other issues to check ( fatigue, other loads: wave, seismic, dents..) ?supplementary loads do need additional thickness

7-Finally if Level 1 and 2 are not satisfactory then one has to de-rate / replace or use level 3= finite elements,....this is costly but more accurate and I believe you are not limited then by restriction of level 1 and 2.

take care .