I am unaware if this is a feature in Arcana, and I am highly aware of the effort that'd be required to pull off something of this scale, but a method of crafting our own spells with the vanilla elements as well as the various elements of the mod (with the potential to easily implement elements from other mods, such as Elithian Races) would be quite enjoyable, not to mention offer a high variety of additional gameplay to tinker with and eventually perfect each player's preferred spell, as well as give Wizard players from RPG Growth their own customizable weapon.
Alongside this, perhaps a chance for friendly (or hostile) NPCs to be capable of casting premade spells of their own (perhaps making it obvious by outfits which ones can and can't, such as Miniknog with experimental looking gear, Florans and Avians in ritualistic garb, Magical Girl Hylotl, Glitch in Wizard outfits, Novakids having Baba Yaga looking outfits, and Humans having a hybrid of these as examples.)