I think every religious bulding which requires a belief shuld have one wonder associated with it. Terracotta Army could use an improvement as it is just old Stonehenge, but later and more expensive, and the Hagia Sophia is very situational because it also increases the
cost of all further prophets.
So my suggestions to improve some wonders would be:
Terracotta Army: Additional free Pagoda (or Monastery)
Hagia Sophia: Free Cathedral instead of free Temple
Angkor Wat: Free Monastery (or Pagoda)
Granted, the Monastery can either be pretty weak or very strong depending on the presence of Wine and Incense, but at the very least youll get +2
and
out of it. Giving a free Monastry to Terracotta Army and a free Pagoda for Angkor Wat would be better for balance but make less sense flavor wise.