Br radical as this person seems to revel in abusing their body.
Put the seat up a full inch and get them to ride 100K, then put the seat down 1" from where it is now and get them to ride 100k. The will find areas of the legs that start to pain, cramp, blow out etc. This will perhaps highlight less than obvious weaknesses that have in other areas that need strengthening.
Strengthen those and then see if their mechanics change and the ITB pain reduces. Medial hamstrings and adductors come to mind.
p.s. I realise this is a bit left of field but it worked for me with some rotation issues last year and felt quite hard core.
