no, that part I would dislike for sure - "or revenge against FL", it's Tai lakorn cliche, please no)
The revenge against the FL wouldn't be dragged out, she will discover the truth soon after and try to fix it while trying to win him back, he will refuse at first but quickly forgiving her then working together to prove his innocence and get revenge. That's definitely better. Do you know of any dramas with that plot?
Great show, I almost gave it a 10. I would've preferred the circumstances surrounding the time he went to prison a little different. For example it would've been better if there was a murder but the ML was innocent, the SML set him up while convincing the FL to betray him thinking the ML committed the crime. Then years have passed, the ML gets out of prison and is out for revenge against FL and SML. Soon after the FL realises he is innocent and they fall in love again while helping him get revenge on SML.