I really don't feel anything wrong with that marriage... There are many points against it
1. Arohi was evil and Abhi should not marry Evil arohi.
Well, They did not show her the evil side much after the leap.. so maybe like Abimanyu she also had her 'redemption'. If people can accept that Abhi is redeemed after few days of emo Abhi Avatar.. then Aru could also change right? And even if she didn't change.. shouldn't this be his exact punishment for impulsively divorcing his wife whom he loves so much.
2. Abhir will call his 'Papa' Mausaji.
Well, this is not the first nor the last time that a man has married sister.. many people still do it. Polygamy is illegal.. but it still happens.. and then the children's mausaji is also their papaji... And there are cases where the a woman ends up marrying her brother in law... then also she becomes chahci to mamma... or the man becomes chacha to papa... I actually do not ind it that icky.. it would have been icky if they were still married and Abhi wanted to marry Aru without divorcing.
3. Aru should not be rewarded for being selfish.
I don't know about this one... If abhi after his 'redemption' will not get punished.. then should Aru get punished after her 'redemption' .
4. Karishma is not a good actress to pair against HC.
maybe... Acting is totally subjective.. and I really did not see much off her scenes to judge her of her acting abilities.. But sometimes when one actor is good, then the whole chemistry is weight lifted by that one actor. Like in Beyhadh.. they cast a man opposite jeniffer winget. That guy..(someone named Karan) was literal definition of one expression. The whole show worked because JW was such a phenomenal actress to pull it off. Maybe with Arohi and Abhimanyu.. If they become one.. then the chemistry will totally depend on HC capacity.. if Karishma is not up to the mark