[New method required] would anyone take a look at this one for me please

https://www.geocaching.com/geocache/GC5BZVG_challenge-variety-pack-challenge

No checker on this one yet, is it too complex ?

This doesn't look like it is possible. There is no method to definitively identify a challenge cache - there are numerous puzzle or bonus caches which contain the word 'challenge' which aren't challenge caches. Unless a method is added to identify challenge caches there is no way to accurately do the checks. The bookmark lists you provided aren't any good as they contain only a small sub-selection of challenge caches (they were last updated in 2014).

no problem, thank you

Hopefully a 'is challenge' attribute/function of some description will arrive.

I archive this thread when it is not possible/allowed