Currently, breeding creatures removes all equipped spell gems and artifacts from both parents, which makes sense. However, when creatures have around 6 spell gems and an artifact each, which are then lost into 30 pages of loot and have to be found and re-equip one-by-one, it can take quite a bit of time. Multiply that by six for breeding your entire party at once, and then do it every few hours, the breeding process starts to take a very long amount of time.
I believe this situation could be made much faster if, like stable groups, you could assign all equip items on a creature to some equipment set. Now instead of looking through your inventory to replace things one-by-one, you can simply choose the equipment set on each creature after they are bred and all relevant items will be equip exactly as they were when the set was created.
Mechanically, I feel equipment sets should replace any equipment the creature may already have equip and issue an error if, for example, there are more spell gems in the set than the creature can have. The interface could more-or-less mirror the existing creature group interface.