I recently started reading through the Shannara books by Terry Brooks, and it got me thinking about how the notion of the wishsong would translate into a system like D&D.
My (very) rough idea right now is a sub-class of sorcerer who can learn spells from any school or class as long as that spell uses only verbal components.
I found a pretty good tool on a site that let me filter to get a list of all verbal-only spells. Level-wise, the list looks reasonably well-distributed and has a decent mix of combat and non-combat spells. That said, I don't have an encyclopedic knowledge of D&D spells and my experiences with the Sorcerer class is limited.
Would these spells be seriously unbalanced when combined with the class features of a sorcerer?
To be clear, taken as a whole, this list will probably still be too limited and will require adding in some additional spells to round it out later. My primary concern is identifying any game-breaking outliers before I start making further changes.
Cantrips: Lightning Lure, Sword Burst, Thaumaturgy, Vicious Mockery
Lvl 1: Cause Fear, Command, Compelled Duel, Dissonant Whispers, Ensnaring Strike, Faerie Fire, Hail of Thorns, Healing Word, Hunter's Mark, Searing Smite, Thunderous Smite, Wrathful Smite, Zephyr Strike
Lvl 2: Blindness/Deafness, Blur, Branding Smite, Earthbind, Knock, Misty Step,
Prayer of Healing, Warding Wind
Lvl 3 Aura of Vitality, Blinding Smite, Crusader's Mantle, Mass Healing Word, Thunder Step
Lvl 4: Aura of Life, Aura of Purity, Dimension Door, Guardian of Faith, Guardian of Nature, Staggering Smite
Lvl 5: Banishing Smite, Circle of Power, Contact Other Plane, Destructive Wave, Far Step, Geas, Immolation
Lvl 6: Otto's Irresistible Dance, Scatter, Word of Recall
Lvl 7: Divine Word, Power Word Pain, Teleport,
Lvl 8: Glibness, Power Word Stun
Lvl 9: Power Word Kill, Time Stop, Wish
This is a significant weakness for the subclass
This list of spells is extremely limited. If you subtract out the sorcerer spells from the new list and compare it to the default sorcerer list, you are trading...
Your spell selection will be extremely limited as a result of this feature. There would have to be sizable compensation in the rest of the subclass features to account for this drastic reduction in versatility.
Another problem is that over the course of a sorcerer's adventuring life, they gain 6 cantrips while your subclass only has access to 4. I'm not sure how you would resolve this, but the subclass should probably account for this disparity.
One possible redeeming factor is the availability of a handful of high-level paladin spells such as staggering smite and banishing smite. These spells are usually only available to paladins of level 13 (for the 4th level ones) and level 17 (for the 5th level ones), but would come online much sooner for your subclass. Usually the only way to get access to these spells earlier is through the bard's Magical Secrets feature.
Bards will get access to at most six of these over the course of their adventuring career (but reasonably only two as the other four could be used for much more powerful options at higher levels), while your sorcerer subclass gets access to all of them. Overall though, I doubt this makes up for the loss of so many spell options.