My analysis:
The opposition outright rejected the fresh elections proposal because
a) They have IK by the scruff of the neck, and would want this political victory.
b) They know they aren't really popular right now with the people, and elections would hurt them. They would want to come in govt, make a sham budget which pleases the people at the expense of the country, get the USD/PKR rate down, and then wait for the people to forget this whole fiasco (which they definitely will). Then elections could be held. Ideally, the opposition would also want to hold out until the selection of the next army chief, but that is a long way away.
As for the foreign interference angle, there is no doubt that the ISI is responsible for protecting our country from such interferences. But, we need to note, an MNA meeting a foreign official, or going to an embassy in itself is no crime. Sure, why the heck would a US official meet Noor Alam Khan (jis ko halqay main koi nhn poochta tha), or Maryam (a convict), or Fazlu, but it isn't a crime.
Same goes with Nawaz Sharif.
Moreover, you need solid proof by way of audio or documentary evidence to be sure that they are colluding with another country. Now, of course no evidence is just going to fall on your lap, you have to work for it.
Another aspect to be careful about, is not to have any flimsy allegation. You do not want to make Nawaz Sharif another Bhutto, and approach this problem with dodgy evidence. Perhaps that is why the establishment and govt is holding back from going all out.
Just another observation.
Rana Sanaullah when asked about NS's meetings, said that "Main is ki tardeed nhn karta, magr aur baat nhn kar sakta, party nay roka hai".
When Kh Asif was asked about this, he didn't deny anything, just said that we cannot afford to anger the US.
No one is denying meetings or the allegations.