We could probably practice it in ways similar to the Eastern Rites: having a large fast before the Feast. Essentially, in preparation for All Saints, we have a day to pray for Christian unity, to pray for the undoing of the Reformation. It could even turn into a miniature “Triduum” about the Church (Oct. 31, we pray for the unity of the Church on earth; Nov. 1, we remember the saints who constantly intercede on our behalf; Nov. 2, we pray for the Church in Purgatory.) And apparently it also has precedence with the East, in that they celebrate the anniversaries of certain Councils (like the “Triumph of Orthodoxy” Day commemorating the end of Nicea II); but it would be more penitential.
my random thoughts as a former Protestant.
-A.M.T. Fisher