I'm presently running into situations where this tag needs to be expanded to be useful for future sets. Either we need to expand it, or make a new tag that is more versatile.
What do we need today:
Pathfinder Wizard Specialists - get all 0th level spells EXCEPT from their Opposition School. Where this differs from SRD Wizards is a Pathfinder Wizard MAY learn spells from their Opposition School, it just costs DOUBLE for them cast.
We need to be able to grant specific spells for Substitution / Subclasses. This is not possible today. Arcanis was rife with the usage that was silently suppressed. Today we have errors.
So, which would be easier - Expand KNOWNSPELLS or make a new tag GRANTSPELLS:
I'm more inclined to go with a New Tag called GRANTSPELLS
x = SpellName
x = LEVEL= (Grants an entire level)
x = SPELLLIST= (Grants spells from another list)
y = Limiter/Qualifier - PRExxx condition that must be met.
Obviously this is a very rough draft, so let's discuss.