Scribing scrolls

Suppose a level 5 mage with INT 16 (+2) has 4 spells in his repotoire. He finds/researches a formula for a spell he doesn't have in his repotoire. He wants to scribe a scroll of the (somewhat situational) spell rather a than replace one he already keeps on tap. Is that within RAW, or are you only allowed to scribe a scroll in your repotoire?

In order to create a magic item, the spellcaster must know the spell(s) that replicate the magic item’s effect, or must find a sample or formula of the item.

-ACKS Core page 117

RAW, the formula of a spell is not the same as the formula to create a scroll of that spell; this mage does not have the spell in his repertoire and he does not have a formula or sample of the item, so he can’t create it. (Also worth noting that he can’t research the spell unless he has a blank spot in his repertoire; also page 117.)

I personally as a Judge would probably allow the mage to do this, but I am not an Autarch.

it would be somewhat costly, but once the mage has made a scroll of that spell once, they no longer have to keep it in their repotoire as they would then have a formula to make the scrolls with.

Okay,  so in order to create one of the situational spell scroll formulas mentioned earlier, he would need to:

  1. keep one spell slot per level free
  2. research the desired spell, but NOT add it to his repotoire
  3. create a scroll formula for the newly researched spell formula
  4. create the scroll based on the resultant scroll formula research

I'm still trying to figure out the most efficient way to do various magical research.

RAW, he would not be able to create the scroll formula without having added the spell formula to his repertoire.

The most efficient method to do this is to find or buy an existing scroll of the spell. Then you have a sample that you can use to create a copy, which then gives you the formula safely stored in your library.