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Description
This may be a big side project for just 'one' spell, but a possible new feature would be to implement the various possible Permanency spell changes to the caster and to others, like the caster giving them themselves permanent Darkvision or Arcane Sight, or giving oneself or another character (presumably one in the same party) or creature Resistance or Magic Fang, greater, or even to Enlarge them.
Beyond the obvious effects, one piece of information that would need to be stored somewhere is the caster level at the time for Permanency spells cast on oneself, since "This application of permanency can be dispelled only by a caster of higher level than you were when you cast the spell."
Side project, perhaps 30 minutes tops. Just have to figure out to implement the user side.