How do we address the lack of wild Aurochs in European rewilding projects?

European rewilding projects are faced with a significant problem: humans drove two large mammals, European wild cattle or Aurochs, and the European wild horse, to global extinction. Self-evidently, such large mammal species are ecologically extremely important. Quite what their effects would’ve been within European wild landscapes we will never know. But we know their absence is ecologically damaging. Their presence would have influence ecological dynamics and succession; so, equally, their absence will be felt within developing wild landscapes.  Within the UK, the European wild boar is also ecologically extinct and largely absent. How should such absences be dealt with in UK and European rewilding project?