Strong's concordance is for use with the Scriptures. You used the term "anti-Christ" as follows:
That list is a list of ANTI-POPES! So the word anti can clearly mean a substitute for something.
A substitute for something in Scripture, yes. I believe you are taking the word anti as used in Strongs and assigning it a meaning outside of Scripture for use with "anti-popes".
Another point - do you maintain the ONLY meanings for "anti-" are contained in Strongs definition?
Strongs gives a couple of definitions. I think the meaning can be found there.
I see no reason to suggest that anti christ and anti pope would use different meanings of the word 'anti'.
Combined with the usage and context of 'anti' in regards to 'anti'popes, I think 'substitution' is a reasonalable meaning and usage of the word anti. ;)