Payback. If India does not stop financing these groups, Pakistan will start supporting Anti State Elements in India. I think the last estimate was 26 groups in India. It will be similar to the 90's, but a lot more ferocious. I pray to God this does not happen as this will lead to a full out shooting war.
Unlikely.
Unlike Pakistan, India has used the intervening 2 decades- from 90's to 2010's - to cement the grip of the Government over the State via unprecedented growth in modern Indian history.
In the 90's, the GoI was reactionary with few police stations and isolated areas with no infrastructure and a Govt tottering near bankruptcy.
Today, the writ of the State is strong in most areas with double the infrastructure(physical and governmental) that we had earlier. Consequently, the ability of anti-India groups to take funding and logistics from Pakistan based elements
sustainably is today
far more limited than the 90's.
Which is to say that even if Pakistan puts its
entire resources behind anti-state elements in India, the results would be
much more modest than what Pakistan achieved in India in the 90's. And India made it through then, with no major damage.
This is not even mentioning that Pakistan was able to support anti-Indian groups in East and NE India using Bangladesh as a launch pad, as BD had an Islamist Government then. Today the Islamist elements of BD have been emasculated by GoBD and India, and are on the run. Their principle opposition - BNP - today says openly that we will no longer be anti-India like we used to be in exchange for support from India.
And also not mentioning that the majority of the Western border with Pakistan is now fenced and lit. The fence has today reduced Pakistan's ability substantially. The need of an electrified fence was felt
because we saw Pakistan's ability to transfer money, men and weapons across the border in the 80's & 90's.
Frankly Pakistan's ability today to inflict damage to India indirectly is
barely a fraction of what it was in the 90's.
Today, Pakistan's entire efforts probably wont bother GoI much apart from their rhetoric in TV to malign Pakistan.
On the other hand, Pakistan today is in the situation that India was in the 90's - a large restive population because of lack of opportunities and social unrest because of Governmental ineptitude and a neighbour that has the means, resources and will to exploit the situation.