I feel like the fire chemistry (two hotheaded personalities) has been done before and so Trisha-Sam would not have been new in that aspect... the whole prince and princess charming couple (which would have been Ishaan-Urmi) has also been done, and even the mix we're receiving now (opposites of nature) has been done...
so I think the show wanted a certain chemistry between the characters but the main point was more to create characters of every personality shade to which we could relate to in some aspect. Once we can somewhat understand their point of view and actions - it would make us more involved in these characters' growth or change.
These individuals have ideals about how their life should be, but life isn't ideal and their lives won't follow any set pattern -there are disappointments, realizations, confusions, misunderstanding, regret, compromises in life that shape how we live it. I think having a fantasy or belief is not necessarily bad but DAK might be angling to show us how these characters react when they have to compromise.
Although, what I truly don't understand is if the CVs felt like they've given us a proper storyline or plot point.. because at this point in time I don't seem to see the real motivation to paying close attention to this serial. What SamUr depict is the very real and large percentage of secretly unhappy couples married for the sake of it ... we've been given characters but now what? The original road block of trisha not happy with the alliance has been moved out of the way, and Ishaan is still playing the helpful friend. what else is there? The saas is even pretty decent and not cruel.