例えば'I wish I had been born as a flower or grass instead'だと直訳すぎて情感が薄い。むしろ'Why couldn't I have been a flower or blade of grass?'と反語形にした方が、もどかしさが伝わる。植物の無垢さと対比させたいなら'To think like this... I should've been a petal on the wind'みたいに比喩を交えても面白い。
'Had I known this pain, I would have chosen to bloom as a wildflower'だと、選択の可能性を含ませつつ植物の自由さを暗示できる。あるいは'These feelings make me envy the daisies in the field'と具体例を出せば、よりイメージが湧きやすい。