If you've read how that Yanfly plugin works, then you should be able to do the same for mp, as what's to be shown by the bar, be it hp, mp, or whatever, shouldn't be a major concern for the bar.
As an example to show that(or in case you want to read more than that Yanfly plugin implementation), you may want to check how
DoubleX RMMV Status Bars works
P.S.: Typically, one would use either Sprite or Window to show the bar. Using the former's usually significantly more performant, while using the latter usually sllows more visual configurations(mainly the bar border)
