I do not necessarily disagree with your premise B. I do disagree though that Spell Versatility is taking away a "vital part" of premise B.
If the party leaves their home village at level 1, the sorcerer has 2 spells they know. The wizard has potentially 6. That is three times the number.
When the party encounters the challenge, between having 2 spells and having 6 spells, who is more likely to have the specific spell they need, right then.
The wizard, because they have more spells available in that moment.
A Wizard with an Int of +4 will consistently have more spells prepared than the Sorcerer knows. And, they do not need to prepare any ritual spells, having them available anyways through their spellbook.
Yes, on a long rest the Sorcerer can swap any single spell from their entire list. But, as I showed, they cap out at having 9% of their list available to them in the moment. Even just counting prepared and ritual spells, wizards have double the amount of spells ready to go than the sorcerer, and looking at the numbers they could have as much as 30% of their entire spell list available within the day. A spell list almost double the size of the sorcerers.
So, the sorcerer is only taking a "vital part" of the wizards ability to be the most prepared if within that massive number of spells known, the wizard does not have the same spell. And of course, this is entirely ignoring the impact of magic items on the two.
I disagree that we have somehow crippled the wizard's position. They have lost nothing of their advantage, the only time when the Sorcerer can take this role away from them is when they were not going to be able to solve the problem anyways.
Okay, I see what you're saying here. And I agree with the value of that particular element of the wizard's versatility. What I'm saying is that there is another important element, which is the ability to gain access to a particular spell you don't currently have access to
the next day.
Or to go beyond that, let me briefly point out the three levels of spell access:
1) Immediate Spell Access: This is almost purely based on the number of spells you can have currently prepared. Spell Versatility does basically nothing to increase the sorcerer's flexibility compared to wizard in this area, as you rightly point out.
2) Tomorrow Spell Access: Standard 5e gives the wizard flexibility in this based on their personal spellbook. Sorcerer gets nothing here. Spell Versatility changes this dynamic drastically by giving the sorcerer their entire spell list (substantially bigger than a wizard's personal spellbook) to choose from.
3) Extended Time Spell Access: Standard 5e gives wizards the same flexibility in this as in Tomorrow Spell Access, with the additional highly campaign dependent ability (which I believe DMs should make reasonably available as a part of wizard identity, but can not be assumed in 5e) to also add new spells to their spellbook. Sorcerers have nothing here. Spell Versatility skyrockets the sorcerer's ability here, allowing them to acquire and cast any spell on the sorcerer list, as well as completely rewrite their personal spells known.
It is completely true that the wizard has a bigger and pretty much objectively better class spell list than the sorcerer. I do not think that invalidates the concerns, since the wizard's limited access to that spell list is of bigger importance when comparing them.
Spell Versatility does not challenge the identity of the wizard regarding 1.
Spell Versatility makes the sorcerer better at 3 than the wizard. This is an identity challenge.
Whether Spell Versatility makes the sorcerer better at 2 than the wizard, depends on assumptions.
The assumptions that some seem to be making is that of combat challenges or
general spell usage. They are about taking a spell you feel is more likely to be more useful in general to the next day's adventure. In this case, Spell Versatility doesn't significantly change the relative flexibility of the wizard versus sorcerer.
However, where I'm going with Tomorrow Spell Access is more about benefiting from
a specific spell (often outside of combat). If that is never a consideration in your campaign, then this may not matter. But if this is ever a consideration in a campaign (and it definitely is in mine) this is a huge thing, because it is a vital part of a wizard's identity that is being taken away.
Highlighted Point: When nobody has the spell prepared/known and we need it,
all eyes should turn towards the wizard. They should
always be the one best able to meet the need for Tomorrow Spell Access and Extended Time Spell Access. That is a huge part of what being a wizard is about. With Spell Versatility,
all eyes turn towards the sorcerer, because they are better able to meet either of those needs, and the wizard only retains that ability with regards to Immediate Spell Access.
In saying that, I'm making a claim that even something that may rarely ever come up can have an important effect on class identity. If anyone can pick up and use a
holy avenger to the same effect as a paladin, that is a challenge to class identity. It doesn't matter if you've never had a
holy avenger in your game.
I understand you may be looking at this as an overall picture of class flexibility. I am too, but I'm also going beyond that into certain particulars.
I'm making a claim that one isolated yet conceptually significant thing that may not change the overall balance of classes can challenge class identity.
I know these are strong claims that I'm making, and I
am making them. Spell Versatility, as described challenges the established class identity of the wizard as it has been established in every edition of the game, and as it has been distinguished from sorcerers in every edition of the game that has included them.
I think it is likely that some players just don't
care that much about preserving class identity, which is why this isn't a big deal to them.
I think Mr. Crawford is completely failing to address Tomorrow Spell Access and Extended Time Spell Access in the manner in which I have explained them.
Let's stop getting sidetracked by sorcerers and bards, then. No one is talking about warlocks and rangers getting the same ability with spell versatility.
A couple things here.
Everything you are saying about rangers is true, but it misses a few points of relevance, which is why people aren't criticizing it as heavily.
The first is that rangers are weaker than paladins in a way they should be (based on tradition) essentially equal. A ranger's spellcasting is inferior to a paladin's, and they get no other benefit to make up for that. The paladin is just a stronger class. Rangers could be given complete access to their class list as prepared casters--identically to paladins--and it would neither overpower them nor challenge class identity. In fact, it would
preserve class identity better than the standard rules do! Rangers already should function that way. So inasmuch as the ranger buffs just make them function more like that, they are good for class identity. I'm not sure I'm happy about how they did it (free casting rather than extra spells prepared--though if they don't become prepared casters, they could actually use some extra oomph of free spell casting to make up for the imbalance with paladins) and that's something I'll bring up in the survey.
The second is the traditional divide between divine and arcane casters, whereas divine casters traditionally have access to their entire class spell list, and arcane casters don't. This makes divine casters very flexible, and useful to the party overall. However, arcane spells generally include things that seem more impactful and less party support on a more regular basis. They have spells that are both more immediately flashy, as well as spells that grant the ability to directly address problems that divine spells generally don't, or to address them in different ways. Illusions, general utility, general use boom-boom. Divine spell lists are highly themed. (In 3e, this actually got quite a bit distorted so that their spell lists stretched quite a bit beyond their traditional core competencies, but wizards had a much easier time accessing just about any spells they wanted to scribe into their spellbooks, and the assumption was that you were allowed to do that (a DM would have to be really heavy-handed or doing something pretty unique to not let you do that).)
Bards, while arcane casters, sort of fall somewhere in between. That's why, even though I'll give feedback against Spell Versatility on the bard (does the 5e bard
need any boosts?) I don't feel like it's a major challenge to the identity of wizards or other classes.
I don't like warlocks getting Spell Versatility either. However, their spell list is a lot smaller than sorcerers, which makes this feature "less" objectionable on them. (They also can't apply it to spells above 5th level.)
Sorcerer identity is the closest to the wizard, and therefore it is the best comparison. Also, the size of their class spell list is the second biggest in the game and almost entirely taken from the wizard spell list. They are the class for which Spell Versatility most strongly challenges the class identity of the wizard.
