を[機「き」]に => Use A as an opportunity N1
Time, Situation
[最中「さいちゅう」] => In the middle of A N3
Time, Situation
たが[最後「さいご」] => Once A occurs, B happens N1
Information, Report
を[契機「けいき」] => As a good opportunity A, (do) B N2
Information, Report