If you're looking for a bit more involvement as a requirement instead of 'afk WB farming', Then you could always throw in needing 4 gifts of exploration for each armor piece as well.
Gives more substance to the 'Pure PvE' armor route. Requires more time investment instead of just AFK, You have to do all the hearts and clear each map a total of 12 times just for 1 armor set. On top of the WB farming, T6 mats, Provisioner tokens, and clovers.