“Sister-Wife” may be the Mormon term, but there is a reason that the Torah calls her a ???.
Historically, even in the time prior to the Cherem, it was not common practice.
Practically, it is a very bad idea for many reasons.
I know it’s a side point, but I must protest the “jokes” employed by some posters to denigrate entire communities of people who have dedicated themselves to Torah, even if their dedication does not measure up to that of the tailors in previous generations. The sole purpose of these “jokes” is to undermine the respect we should have for people who spend significant amounts of time learning Torah.