2 回答
Things that we would never have imagined take place.で問題ありません。
Wouldは可能性を表すものという認識で間違いありません。
Things that we would never have imagined would take place.でも文法的に問題ありませんが、意味ニュアンスは若干違います。
Things that we would never have imagined would take place.は、例えばIn another universe, things that we would never have imagined would take place. のような、可能性のニュアンスがありますが、
Things that we would never have imagined take placeはThings that we would never have imagined DO take placeという雰囲気ですね（そのthingsが実際に起きている）。例えばThings that we would never have imagined take place everydayなど。