This sounds like it's going to be an interesting project.
As far as possible OpAreas go, choices are somewhat limited by the fact that Russia only has 4 points of access to the worlds oceans: the barrents/arctic, the baltic, the black sea, and okoskt. Chosing between those is going to depend on your backstory and the tactical situation you want to create.
As far as backstories go, your strongest candidate is the Baltic, followed by the Black Sea. Russia has been freaking out the Baltic states as of late, and with a little bit of imagination, you can apply similar pressures in southwestern asia that might cause Russia to come into conflict with the Ukraine, or more likely, Georgia, Azerbaijan, and Armenia. Turkey would likely side with G/A/A over Russia, which means NATO has access to the Black Sea. The barrents isn't bad, but the White Sea (S. of arctic, E. of Barrents) and Okhost don't seem to be areas where naval conflict is plausible.
In terms of assets, the Barrents is strongest, since that's where most of the sub fleet is based--akulas in particular. Of course, with a little bit of strategic pretext, those assets can be redeployed. The Black Sea is going to be the worst off in terms of assets present without being redeployed, sub assets in particular.
Tactically speaking, I think depth is going to be a consideration, since you'll probably want a layer to play with. This will be a major blow to the baltic and barrents. It'll hurt the White sea as well, but it does have some deep canyons. The Black Sea and Okhost can both get quite deep.
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