I could argue that a new mastery could be a minor virtue.
For example - Barbed Mastery
This mastery allows the caster to add his Mastery score to the damage of any +X damage spells. so Crystal dart would with a mastery of 3 allow a caster to throw crystal darts which did +13 damage not +10. This may seem like quite a low powered breakthrough, but it could be a significant boost to someone with mastery 4 (50 xp easily started with by the mastered spells virtue) including penetration and multicast. Multi-casting 5 Pilum of fire with +4 penetration and +19 damage. Quite a jump that could easily take into account a few size wound range modifiers and may make a light into a Medium wound or medium into a Heavy, or make several mediums into heavy. in this case giving a wound penalty difference if all 5 hit and were bumped one grade of damage of 10 Pts. If this was against a Size +2 enraged bear soak 10 .... (assuming equal and average dice rolls) then the bear would take 5 pts of damage from the non barbed spell and then take 9 from the barbed this means either 5 light wounds or 5 medium wounds. Making the bear on it's next attack at either -5 or -15 to its attack.
I would also argue that for directly damaging Perdo spells, that a similar mastery could be mastered to overcome size. It would mean that a normal spell geared for size +1 and lower could actually be made to have relevance for bigger sized animals. So much that the mastery would directly add to the spell it could affect. So a Level 15 blunt the vipers tooth (I think that's it's level) which effects animals up to size +1 could be geared up to effecting larger creatures without having to relearn a spell for successively larger creatures. So this above spell with a mastery of 4 could effect up to size +5. So most animals and most larger versions of conventional animals would fall into this.
I would argue that the 30 breakthrough points and time spent developing these mastery specialties as well as then spent learning them more then offset the gain received from improving arts and relearning new versions of the spell.
I would say the theory to bring this to the world would fall into a similar vein as flexible formulaic magic.
These things however could represent knowledge which has been shared with the order as per the Colloquium Delectorum
A