OK, if there is no Ivan IV or his exact replica, then there is no his Livonian War and most probably no PLC (was created to stand up to Ivan's aggression against Lithuania). Muscovite state is less exhausted and most probably has better relations with its Western neighbors. Now, let's put things straight:
(a) There was no succession crisis after Ivan's death: the crown went to his son, Feodor.
(b) There was no true
crisis following Feodor's death: Zemsky Sobor elected Boris Godunov without any noticeable challenges/
(c) Boris ruled for few years without any problems but when the weather was bad for few years in a row with a following terrible famine and massive hunger deaths situation became ripe for the popular unrest. Name of "Dmitry" was just a convenient one: in OTL pretty much every massive rebellion had its own "royalties".
So you want what? "Ivan doesn't come" but who does? His brother Yuri of Uglich or some other figure real (Yuri Ivanovich, Andrey Ivanovich) or fictional? You have to be more specific. Then, who are "the other powers"? The PLC does not exist, Lithuania is too weak for conquest of the Muscovite State, Poland does not have common borders. Sweden just got a new dynasty and has other problems besides starting a war with Moscow (not that it is already a major military power).
And the bad weather still has to be there.
The only power capable of realistically attacking Muscow is the Crimean Khanate and this was mostly about the looting and/or formal acknowledgement of a vassalage. Khanate of Kazan is already ruled by the client of Moscow.
Sorry to say so but you are a victim of the stereotypes (

): an idea that Peter's war for the Baltic coast was something related to being "progressive" is a popular stereotype with no traction to the reality unless you are going to define Ivan IV and Peter's father as "the progressives": both of them had been trying to conquer these areas. Ivan IV even tried to build up a navy based in Narva. Fighting there was a traditional thing, return of the "ancestry lands" (flimsiness of the claim seemingly did not bother the Russians) .
Then goes the terminology: "conservatives and reactionaries" is a nice slogan but in this context it has close to zero meaning except for the Old Believers who are rather irrelevant within the context of rebellion and balkanization . Practically all "who did matter" were not the "reactionaries" since the reign of Alexey because innovations already had been there and the Russian nobility liked these changes.
That's nice. You don't know who these "reactionaries" were but are sure that they had much sway on him. Well, at least one of the most important people implicated in Alexey's Affair, Kikin, was quite progressive. You can easily find his short bio on Wiki and find out that he was an important participant of the Peter's reforms and his main sin was that he was taking Alexey's side (not a big surprise because he had an earlier quarrel with Menshikov). Another implicated person, Vasily Dolgorukov, had some disagreements with Peter and after Alexey's affair was demoted and sent into exile. But he also hardly was a "reactionary" and during the reign of Elizabeth became President of the College of War and made significant improvements regarding the organization and logistics of Russian military.
During Poltava campaign Alexey was in change of improvement fortifications of Moscow but even if we assume that stuff about the "weak peace treaty", this hardly has anything to do with the "balkanization" or anything of the kind. His father lost Ingria but, AFAIK, Tsardom did not fall apart. Defeats in the wars were quite usual and somehow Russia did not fall apart after defeat at Narva or quite a few other defeats preceding Poltava victory. Neither was Peter assassinated or ousted. So you are in the area of a free flight of a fantasy. What if each and every ruler in Europe is assassinated simultaneously? What if Charles XII is assassinated? Etc.
Speaking of the relatives, there were 3
legitimate daughters of Ivan V and by that time, after the regancies of Sophia and then Natalia, woman on the throne was not a complete impossibility.
If you are talking about the future Catherine I, her marriage of 1707 was secret and until 1712 she did not have a claim. Catherine Ivanovna in 1709 is 18 years old so if she is a candidate, there can be a short regency or no regency at all.
What Frederick William has to do with anything I have no clue. As for Karl Leopold, how about checking the dates before posting? Catherine Ivanovna got married only in 1716.