Kirilenko as successor?
How would he be?
Kirilenko declined pretty badly in terms of mental faculties, so he would not have lasted long. He was high-handed, had a tendency to be tongue-tied even in his prime, and had a hard time communicating his ideas when the spotlight was on him. He would have retreated behind a desk and try to put together a team of his people to run things for him. But per the memoirs of his peers, Kirilenko had the hardest time putting a crew together. Now, Kirilenko was himself part of Brezhnev's crew for Brezhnev loved to form factions of various people he'd discovered in the '40s, '50s, and '60s as he was moving up the ranks, and Brezhnev would take them with him each time he'd get promoted. Kirilenko moved with the flow and rose with Brezhnev, but unlike some of Brezhnev's crew who then formed their own crews, Kirilenko had a hard time finding people. This is pretty remarkable given the high-positions Kirilenko held. He was for a while pretty much the head man of the Soviet military-industrial complex, running everything from factories, to construction, to even space camps (for a bit).
Kirilenko should have a good-sized faction all about him by the early '70s. Instead, he had to rely on Brezhnev's people. And this caused problems, because him and Brezhnev began to disagree on Soviet economy in the mid '70s. Kirilenko wanted "reforms," but was rather confused on what those reforms would constitute. Brezhnev just wanted to wave a magic wand and for things to "improve." Should Brezhnev have died in 1975, Kirilenko would need to use Brezhnev's crew to keep himself afloat. But this would have invariably limited him and he would be seen as Brezhnev 1.5
It was said Kirilenko was opposed to the War in Afghanistan. This is mostly extracted from Kirilenko's harsh words regarding the leadership of the Afghanistan Communist regime. Kirilenko thought them idiots who mishandled a sensitive situation and caused their own problems, which the Soviet Union was now having to resolve. This view was shared by others. But this could have just been Kirilenko venting about the money spent on Afghanistan, as every ruble sent there meant less money for his ministries. I am not sure how much Kirilenko would have done to avoid the Soviet involvement in Afghanistan, but there were more than a few Soviet politicos who balked at the money their puppet regime in Afghanistan was asking. Before the Soviet Union became truly and fully military involved, it was asked to forgive loans, extend more loans, and pay off other loans of the Afghani regime. Would Kirilenko have put his foot down on purely economic reasons? Hard to say.
Kirilenko was a reactionary Brezhnevite through and through, with occasional moments of maudlin romanticism towards Cossacks (he spent considerable energy and political capital to get a holiday going to recognize some Cossack tribes for their contribution to the Soviet regime and WW2), and would randomly favor this author or that, including those he felt were overlooked. The latter would sometimes be embarrassing as he had crabbed tastes, and would champion authors he was told were good without actually reading their works. Some say he partly did this to needle the Ministry of Culture and to show he could push them about.
Kirilenko did not say one word about environmental damage of a major polluting factory, because he felt the project was sanctioned from on high by Brezhnev himself and he dared not move against it. And he regarded environmentalists as problematic rebels. But then, on a whim, he saw a documentary about how the small government fisheries in Lake Baikal have caused some environmental damage to the area and the fishing villages in the area, and he personally intervened to stop the dumping of pollution. So Kirilenko could have been capable of lessening the damage done to the Soviet environment, but only if the pollutant was not a major electrical station, or a nuclear reactor.
Kirilenko had under his competency "closed cities" - towns where secret military research was done, which did not appear on maps and had no names, merely codenames with a numeric designation. At no time did he seem to show any inclination of learning what was happening there, for good or ill, and how things were run. People who worked with him thought him to be rather ignorant about nuclear science. Not saying he starts WW3, but he thought of nuclear weapons as just another weapon. He was pretty limited in terms of his intellectual capacity.
Kirilenko once spent an entire weekend reading secret reports about UFO sightings which he asked about from the KGB, and at the conclusion of it allowed a newspaper to publish a story about a UFO sighting in West Germany, as well as a UFO sighting in the Soviet Union. Many a tea leaves reading of this incident was had, including by the KGB themselves. Some thought the old boy was losing his marbles. Others thought it meant he was pro-press freedom (he showed no wish to return to the Thaw at all, and was reactionary). And some simply chalked it up to a weird bug bear. Take it as you will.
The most defining characteristic of Kirilenko's spells as chairman of the major committees was his belief that within the walls of the Kremlin, among Politburo members, total truth should be had regarding the state of the country. But none of it should be shared beyond the walls. Thus, he had no problem taking a brutally honest report on bad harvests, and stagnating economy, but was most concerned about it being leaked. His peers thought the former highly suspect. The feeling was that even within the Politburo, one must bullshit and put a happy veneer on the bad news. Kirilenko's approach ruffled feathers. And some say that was the whole point. He wanted to make other ministers uncomfortable, to show he could put the boots to their ministries . It made him few friends. And contributed to his inability to form a faction.
Kirilenko would not have lasted long. His mental health was already showing signs of being troubled toward the end of the '70s. He would have been a winter king. But he could have changed things. I doubt he would have resolved the economy. But I do think he may have not gotten the Soviet Union involved in Afghanistan, because he regarded himself as his own foreign minister, and was not above second guessing foreign ministry work during his frequent foreign trips. That alone would have changed a great deal.