I am coming a little late into this discussion.I thought I will add my two scents to this discussion any way.
I do not think any of us know the real reason for P's exit from the show.
In a situation like this there are always two sides to the story.The truth lies somewhere in between with both the parties being partly correct.
As for replacements they work provided the transition is made seamless.Here for reasons unknown they were made to make a transition.Since is is so sudden they should put in extra efforts to make the transition more convincing or continued to make the new actor portray the character in the same as the previous actor.At least that would have ensured continuity and consistency.
When I say the portrayal should have been similar to the previous one I do not mean that she should imitate the previous actor.
This abrupt change in the characterisation coupled with a new face makes it difficult to the viewer to adjust.
When Pratyusha came in place of Avika as a grown up Anandi she was nothing like what we expected of grown up Anandi because changes have been made in the characterisation though the basic character remained same.But the change in the way the character was portrayed was not explained well so many people stopped watching after the leap because they could not connect with Pratyusah's Anandi But slowly it picked up because of the strong storyline and the improved performances by P and Shanky.
I hope they do the same at this juntcure also ensure that the performances and the story line remain strong inorder to ride this storm that was created by the exit of a team member.
Ultimately they are selling us a show that is a joint work of writers directors and the actors.
If they want to prove that no single person is bigger than the rest of the team they should step up to prove their point that performances story and characters are more important than anything else in show business.
Coming to replacement of actors like Surekhaji If they can't find a replacement for her they will end the character because it is near impossible to find someone who can take her place and also because though her character is a very important character it is not a lead role.
Just like Gauri if they cannot find a replacement for her they would rather end the track than replace the actor because she is not the lead.
In case of lead they have to go for a replacement because the story cannot move forward without the lead espicially when you have so much story to tell.
As for shows like IPKND it is a romantic story other than romance there is not much else happening in the story so they have to shut down if the lead decides to quit.
In BV it is the story and the characters that made the pair so special and the setting in which the love story was happening is what made their story and the pair so appealing.
The new actress has to capture the essence of the story and the character to make the magic work.
Replacement will work in favour only if the replacement and the rest of the team make it work.