I am pretty sure I have read @SamMe Suggest it somewhere as a QOL improvement.
I really hope that SG would consider allowing us to reset Troop Levels. Maybe Similar to Emblems?
To get a 4* Troop can (and Usually does) take forever.
Personally I have no Purple Mana Troops. All the other colours have Crit Troops at almost lv 23 and only recently started getting Mana troops in the other colours. I however know that it takes a boat load of resources and 224 years to level another troop to the Magic Lv23.
I would reset all my Crit troops in a heartbeat, if it were possible to do so…