Dipika u read my mind, Sulehka is indeed a major obstacle in sinal reunion.
Forget about Richa , if Richa tries to create problem in sinal reunion , it can be solved, by exposing her or Kunal can ignore her like he always does( don't wanna discuss about his , i would end up writting an essay ).
About Veena , once she comes to know about Richa's truth , we shouldn't worry about veena .
But Sulehka , she can be the trouble maker for sinal and their kids , i won't call her a negative caracter, but she would try to distance sinal for the sake of her son. And here sinal will have to face problems : As Sulehka is the one who raised AD when sinal weren't with him .
Sinal , specially kunal is indebted to Sulehka , as they ( diwans ) raised his son, sulehka was with sidhi when she needed someone's support and most importantly Sulehka got sidhi out of jail ; so Kunal will have to show gratitude towards her ( of course if hid ego doesn't get hurt !)
Im sure once kunal comes to know about the truth , even if he wants to reunite his with wife , the fact that he is indebted to Sulehka will become his major problem , as sulehka can emotionally balckmail Kunal or Sinal !