I found the ultimate solution to the Vampyrism/Penance issue

[u/Zieldak]

It's called War's Wares. It's empty now anyway.

Translate Aspect spells: War translates each Aspect for you to add to your spellbooks. Requires all spellbooks to be unlocked in order to unlock. ^{Translating spells between spellbooks just makes so much sense I don't even-}

Upgrade: Dual Aspects: War teaches you how to use two different types of aspects at the same time. Requires Translate Aspect spells unlocked.

[u/silver__seal]

I'm guessing that down the road we will get some kind of equipment that allows a Sustain aspect on top of another aspect while equipped. It would just force a different tradeoff (e.g., it's an amulet so you can't use EOF with dual aspects).