Is it imbalanced to change a Warlock Subclasses' Expanded Spell List to Additional Spells Known?

Question

Warlocks have a relatively limited number of spells known, and (in my experience) the fewest uses of spells throughout a given day in a campaign. I feel with these limits, it would not be unfair to instead of expanding their spell list with the 10 or so spells from each subclass, actually add the spells to the number of spells known. There is precedent for this, as the Sorcerer subclasses from Tasha's Cauldron of Everything both add spells to the number of spells known, and all of the cleric subclasses add permanently prepared spells to their lists. The only exception I think is needed from this house rule is the Genie subclass's access to Wish, which I would consider an addition to the spell list, instead of having 2 spells available for the ninth level Mystic Arcanum.

Because of their limited use of spell slots, expanding the Warlock options of what to do with those spell slots I feel would not hinder the balance of the game. Is there some balance level that I am missing?

Answer 1

I think that would not be unreasonable. More spells known adds versatility more than it adds power, and thus should not affect balance much.

My own houserule regarding this is to add a PC's primary stat bonus to the number of spells known. Classes that prepare spells (cleric, druid, wizard, paladin, artificer) all already have that bonus built in -- they get to change their spells every day, and have those extra spells to prepare. Meanwhile, the classes that know spells (sorcerer, warlock, bard, ranger, eldritch knight, arcane trickster) are stuck with both fewer spells, and no flexibility in them. So adding the stat bonus to the number of spells known helps them to be more versatile and useful casters, without giving any imbalance of power. I also think it makes them more fun to play, as they can be useful in more kinds of situations.

This seems to be enough of a change to help the situation without going overboard, so I would not do both this and add the expanded spell list, but even doing that isn't absurd. Clerics, for example, already get both their Wis bonus added in prepared spells, plus the spells from their domain added.

As an aside, in my world I also changed the ranger spells to work like paladin spells, so they get 1/2-level + Wis in number, and can prepare them each day. This helps the ranger to be more useful, and closer in effectiveness to other classes.