Yep, I'm planning to have fun with spells to begin with. And unlike the quest system which was practically invisible until it started working, spells have tons of visual stuff I can work on right away.
It's the effect system I have my heart set on to begin with. Effects are the building blocks of everything - they're atomic and physically do something
inside the game. Just like a quest is built from many atomic actions, a spell is built from one or more effects. For example, a vampiric health spell might combine a health damage effect to Entity A (target) with a heal effect to Entity B (caster). That's just an example, it's probably easier just to make a vampiric effect that does both parts, but you get the idea.
What I want is for magic to be at least partially scriptable. Not to the extent of quest system, but enough that users can easily create new basic spells by combining multiple atomic effects. And then modders can inject new effects in the way they can inject new quest actions now. Wouldn't it be great if rival vampires could levitate after the player over rooftops? Or monsters could support each other with heals? Or ancient liches could summon skeletal minions and raise them back from the dead?
There's so much cool shit that can be done beyond just reimplementing Daggerfall's standard spells. And that's my real starting point - to create that effect potential. Then everything else (potions, magic items, spells, etc.) all build onto that framework.
And the potential for screenshots and GIFs is outrageous here. It's gonna be fun.