Does Lithuania rising in Muscovy's stead count? I forget exactly how but I had a professor for a Russian history course who claimed that to be a very reasonable alt history but I can never remember when he claimed it was most possible.
A stronger Lithuania I would think would eventually seek Latvia and Estonia, especially if it continued encroaching into Russian/Ruthenian lands like Vladimir and Novgorod.
1) there was no muscovy, estonia, latvia, lithuania at the time. If we want to be historical, there will be Novgorod and russian khan dependencies+Rus if we go back enough, Couronians and semigallia and lettigalia instead of latvians, ingrians and liiv instead of estonians, samogitians and jotvings and others instead of lithuanians. Its obvious that lithuanians will still be lithuanians as in OTL, but it becomes more difficult as we go north. Semigalkians were a regional power due to trade and military while curonians were the late-vikings but lettigalians didnt excel in anything great. Its possible that there would be either united "latvia" under Curs or Semgs, but unification would need to happen prior millenium before they become too distinct. The same with estonian region.
2) As i said, Rus tried to invade baltics a lot earlier but failed, so thats pretty much impossible.
They did get beated on for quite a while, Russia tried pushing from the east, Germans and Poland from the south, while Denmark and Sweden came across the water landing in the west or north.
They was repeatedly battered from multiple sides with no allies, and if anything a unified Paganistic Balticum would only become a lightning rod for even more aggession from Northern Europe, with more of Northern germany, and prehaps even England deciding that this is a more convenient target than sailing to Middle East, seeking religious glory, and in the case of second sons, land. I might even state that the reason they survived as long as they did was because only their closest neighbours bothered crusading against them due to their disunited, small size.
King Mindaugas. The first and only king of Lithuania adopted christianity and survived the northern crusades. I hope you have heard of him.
Also, as i mentioned earlier, the unification would either be a loose federation like germany or USA or it would happen by force. If it happens via federation, its obvious that tribes will compete in "a race to the east". By that i mean that there WILL be an organized invasion to Rus to strenghten their power. It means that we would expect Latvia to the moscow, lithuania to the kiev and prussia to the... i dunno. This is where it falls apart. PRUSSIANS will be the sick man of baltics. It WILL be the one to atract christians, but, since they are locked from expansion, they will seem relativly weak considering we have a fed, so germans and poles might think that baltics are FFA. This could go either way from here. Either baltics adopt christianty (at least pretend to) or they fight and lose. Remember what i said about Mindaugas?
Second option is force, and this scenario only delays OTL, since its basicly the same situation, instead there is only one head.
I hope this answers to your questions.