Perhaps, but much as we try to say that tz abbreviations are inherently ambiguous, MSK does have a well-established and far-reaching meaning outside the context of our project.  Moreover, our own guiding principles would suggest use of BYT (for "Belarus Time") or MINT (for "Minsk Time") before considering anything else.

In fact, this is what was first proposed when Belarus switched to year-round UTC+3 in September 2011:

Only when Ukraine announced intent to join Belarus on year-round UTC+3 a few days later did we decide to use FET as a convenient method of grouping:

(Admittedly, we created FET because we thought at the time that it might become more common and needed a distinct name.  In the end, we only grouped Belarus and Kaliningrad, as Ukraine did not follow through with that plan.)

Now that Kaliningrad is on year-round UTC+2 (EET), this leaves only Belarus.  It does not make sense to keep an invented grouping around to group one thing, so FET should go, and it has.  But it equally doesn't make sense to group Belarus with Moscow just because Moscow changed its clocks.  I may be wrong, I cannot think of another case where we have applied the designation of a neighboring country to a region that has not itself changed its timekeeping rules.  In any case, it hardly seems appropriate here.