So we have unique companion armour for Astarion, Shadowheart, Halsin, Mynthara, Laezel (somewhat unique), Karachi. It gives the characters their own look and fits them very nicely.
Unfortunately it becomes obsolete very quickly. Only one companion has a nice swap of armour due to story.
Maybe there could be a way to upgrade their armours by upgrade kits? After all, functionality for this is already implemented (see combining dye with armour).
So for example, you reach act 2 and can buy something like "reinforced leather patches" that you combine with Astarion armour and it becomes armour class 12+1
Would be nice