Well you have to look at this case in more idealistic form. Moreover you have to apply various conditions.
If we talk about reality than out internal affairs are more than enough to keep both nations in the state of war. Our clashes are too deep and too dense and spread in almost every field of life. In my sight it is impossible to restore a long lasting peace between India and Pakistan even if we completely ignore the foreign factor.................
In current case we are dealing with hypothetical case so lets make few assumptions.
Like you said Internal factors are ignored, suppose by some miracle they all are resolved with peace.
Now we have to look at foreign affairs only and find the Third party who don't want to see as friendly and co operating nations. As you mentioned three cases, I will put China and Russia in one pole and call them REDS, and put USA and its allies (Japan, Israel) in opposite pole and call them BLUES.
Assume that both Pakistan and India are now friends after solving all their internal issues. Call them as IndoPak.......
Now we will discuss both cases hypothetically and try to find out what will happen in each case.
CASE 1: Indo Pak are pro Reds and Hostile to Blues
Lets suppose after peace treaty both Pakistan and India decide to bend towards Russia and China then ofcourse it will increase their distance with Blues. Both Pakistan and India will have to make few harsh decisions on geo Politics to Win both REDS. India must have to lose Japan and other its allies in South East Asia and Oceaiana for the Sake of China. Doing business with China means you have to lose Japan. CPEC will prevail and economic markets will develop in both countries but we will see mostly Russian and Chinese product. All these four strong nations enhance their co operation in the field of economy (own banking system), defense ( co operation in defense systems, joint virtue), more geographic depth, more vast resources and man power as well as diversity in talent. Afghanistan, Iran, Napal, Sri Lanka, Bangla Desh, Bhutan, Berma and others will join up creating a mass blob of countries working together in direction of their overlapping interests. Both Russia and CHina will get more secure trade routes and as both Huge Economies of China and India will resonate together, it will enlarge to many times and pose drastic threat to industries and economies in Europe and Unites States.
As it will not be easy and NATO will try to poke nose, so an alliance of China, Russia, India, Pakistan, Iran will be more than enough to neutralize NATO influence. Using influence of Pakistan, Arab countries can also be attracted towards new Asian Pacific Alliance (APA). It will pose grave threat to Israel and Europe directly and to North America indirectly. It will change the geo politics of Latin America where many countries like Argentina, Venzvella and Brazil will become new working grounds of co elaboration for APA.
It will pose many threats too, like Sunni Shia sectarian issue can dominate if Arabs decides to stay in NATO pole. India have to lose Israel and Pakistan have to lose KSA if necessary. But if they agree to join up then it will help in a better way.
This Case looks very charming for us but pose grave threats too. Like it will make World Bi Polar once again and ''hot Bipolar'' to be more honest. Series of clashes or hostility if ever brought war then it will theoretically drag each and every country to World War resulting in devastation which can not be imagined. United Nations might collapse and new ''Talking'' plate forms will emerge inorder to ensure dialogue and avoid armed conflicts. Worth noting part is that almost 80% of World population will be in APA and its allies while rest in NATO and related countries
CASE 2: Indo Pak are pro Blue and hostile to Reds:
Now this case is bit crazy, why because we have United States as our allay which make this Case bit complex for reasons we all know already. Indo Pak are looking towards Europe and USA and want to keep distance with China and Russia as they both think that both REDS are creating violence between them. United States as usual help to agree, offer new opportunities in almost every field of life and mean time bring its new battle group bit closer to our shores .
Now as Pakistan and India are together, so winning Bangladesh, Afghanistan, Sri Lanka,Nepal is not a problem. We will become more friendly with Arabs and Israelis but hostile towards Iran, Iraq, Syria axis. This new strong ally of NATO in south Asia pose direct threat to China and Russia, using Influence of Indo Pak and NATO the trade routes for China are also tightening in South East sea and Economic challenges for both REDS is rising their heads. It will bring China, Russia closer, like Twins. and who will be on front line to face those Twins? Europe and Indo Pak.......... USA will use Europe to isolate Russia and Indo Pak to challenge China both economically and strategically. I actually have no need to explain it further, just consider case of Japan and South Korea here. Indo Pak will be like them, developed, progressed but an angry neighbor with nuclear weapons with volatile mood.
So will it be REDS or BLUES.??? WHo Knows. But real question is what will happen after friendship? What will be the deciding factor that with whom we will side? In my point of view it is unlikely that both Pakistan and India will come to a peace treaty all alone, ofcourse their will be third party, RED or BLUE or may be combo of that. But the one who will take the most effective and wise role will win the Alliance of Indo Pak and hence the situation continue according to both Cases I mentioned.........
Last Note: It was all just my imaginations and hypothetical analysis. But answer remains.......... who don;t want to see Pakistan and India as friends? China? USA? ............... I believe BOTH. I will call it a DRAW. Both of them don't want to be Friendly States as it will bring a risk of choice, either win huge geo political advantage as friend or lose every thing. And ofcourse the losing side will try ''Unfair'' mean to derail every thing, either it is United States or China.............
Hope you enjoyed the read
Lets hope the BEST THING HAPPEN ................
@WAJsal @Stag112 @PARIKRAMA @MaarKhoor