Well, I can get all of Muscowy+missions (including vassalizing Novgorod)
Make myself HRE, and vassalize everything in the HRE, vassalize all of France, all other small monarchies outside France and HRE (Cyprus, Crete, Corfu, Naxos Sicily, Navarre etc)
Also whatever I can get in between Muscowy and the HRE. (Obviously I would get Hungary and Croatia and whatever else to border him)
And then I would ally myself to all my vassals, and perhaps what other strong catholic nations there are. Build a great army...and just deeeeeeclare war.
And yeah, all that before 1450 at least.
And I would surely like to see the Ottoman-player who have gobbled up all of mamluks, timurids, golden horde *aaand* conquered all those western provinces I mentioned before 1450.
EDIT: Might be possible to do that as Ottomans...I've never tried.
Nothing you mentioned is in anyway something that muscowy is especially good at, for diplomacy there is Austria (catholic, +3 Diplomatic skill), for war there is Castille (starts strong), Ottomans (start even stronger and have an awesome cb against europe), England/France (once you eliminate the other you have practically one the game), Burgundy (awesome sliders) etc.
Muscovys strenghts lie in their masses of troops, the possibility to just escape europe eastward, the low maximal warexhaustion and other smaller things, none of which you especially use, if you want a country that is protected nicely you should take England, since muscowy's "protection" you always advertise is basically a gigantic unstoppable mass of nomads, at least very early in the game....