I was curious of the reasoning for Armory not supporting Paragon and found my way to a reddit post which seems to cover the topic quite well… a comment by OakFern.
The assumption in the linked commentary seems to be that either newly allocated points are unallocated or Armory has to not support Paragon and that the decision comes down to choosing the lesser evil (least negative impact to players).
An alternate solution occurred to me while reading.
Scenario: An Armory save is done at 1000P, then the player levels to 1200P while putting together a different build that lacks toughness so moves 50 paragon points from Mainstat to Vitality along with the extra 200P that goes into Vitality.
The player saves the new build at 1200P, then Equips the 1000P build to hero.
With that, 200P remains in vitality (when the player remembers, its at their discretion to reallocate and resave or not), and the 1000P Armory save restores just the 1000P of paragon allocation at the time of saving, including restoring the 50P to Mainstat.
The player can flip back and forward between the 1000P / 1200P Armory saves and everything is in it’s place.
Does this adequately address the balance of compromises or have I overlooked an important case that would be a pain?
An alternative is to roll with the unallocate unspent points at the time of the 1000P, retrigger the Notifications star on the Paragon tab and player spends the paragon and resaves the Armory set.
Either of these seem better than having to remember paragon settings when switching armory sets which is the current do nothing approach.