Yah, if Urmila's kalakari had succeeded in convincing Kokila that Rashi was a docile godly girl, she would have picked her for Aham and it would have been good to see how Rashi would handle Aham...but I think when finding out he was in love with Anita, what would Rashi have responded with? It would have a whole different drama.
But I feel had Aham married Rashi he would have been happier too, as she was educated and not such an embarrassment to him, she has Gawar characteristics (touching the floor in Swizerland, commenting that the car has no engine). He still doesn't mind her, so I suppose he would have tolerated her better.
Gopi just wanted love from everyone so yes, it would have been good for her, an orphan, ill-treeated by her step family to go to a loving saasural, instead she got more abuse in her saasural, but I feel had Gopi been stronger, she saw how hurt Rashi was with Kokila picking her, she should have declined the marriage proposal in the first instance to Kokila give her back her kangan, after all Kokila rejected her sister right and that very rudely, pulling her saree off to reveal jeans underneath...she came with too much attitude in the Shah's house, maybe it's the situation in Indian families when daughters reach marriageable age, and they married the two girls without any dowry right, so they tolerated this attitude from the Modi's. But yes, Gopi deserved soft hearted Hetal as her saas and Jigars love.