Why must the choice of an Arcane Bond be permanent?

Question

What game mechanic breaks if my wizard chooses a Bonded Object at level one, then has that object broken and destroyed at level 6, then at level 7 chooses to take the Improved Familiar feat and create & gain a Homunculus?

I understand the rules say one or the other for Arcane Bond: Familiar or Bonded Object.

At 1st level, wizards form a powerful bond with an object or a creature. This bond can take one of two forms: a familiar or a bonded object. A familiar is a magical pet that enhances the wizard’s skills and senses and can aid him in magic, while a bonded object is an item a wizard can use to cast additional spells or to serve as a magical item. Once a wizard makes this choice, it is permanent and cannot be changed.

What I don't understand is why that choice must be permanent. What huge advantage does a wizard get with the flexibility to shift once over his adventuring career? That wizard is giving up one class feature for a different class feature.

It seems to me like the Fighter has some flexibility....

Upon reaching 4th level, and every four levels thereafter (8th, 12th, and so on), a fighter can choose to learn a new bonus feat in place of a bonus feat he has already learned. In effect, the fighter loses the bonus feat in exchange for the new one.

... as does the Sorcerer

Upon reaching 4th level, and at every even-numbered sorcerer level after that (6th, 8th, and so on), a sorcerer can choose to learn a new spell in place of one she already knows. In effect, the sorcerer loses the old spell in exchange for the new one.

Is the wizard's Arcane Bond different from these examples in some way?

---

Answer 1

I can see two reasons why the wizard would not be allowed to change her arcane bond.

Mechanical aspect

The main difference I can see between the fighter / sorcerer example and the wizard is that a familiar provides a constant, specific bonus.

One of the risks would then be that the wizard changes familiar depending on the current focus of the campaign. For example, he would start with an armadillo to protect against attacks, then face more spellcasters and replace it with a dodo for the initiative bonus, later change to a pig because the campaign has more social encounters, and so on.

I always assume that the reason fighters and sorcerers can change their class features is because some feats and spells don't scale well. Wizard bonuses don't scale at all, so this concern doesn't exist.

Flavor aspect

Another difference is in terms of flavor: the wizard is bonded to that item or familiar. Another class that has a bonded companion is the paladin, and while a paladin can change her bonded mount, it takes 30 days during which she has maluses to all her attacks.

On the other hand, there is no connection between a fighter and its feats or a sorcerer and its spells.

Would the game break if the wizard was allowed to change its arcane bond, then?

Probably not. That's, after all, the reason it is included in the retraining rules.

However, other players could get jealous that the wizard gets a flexible bonus that can be changed over time. A ranger might wonder why he can't change his favored enemy, a cavalier might want to change his order, and so on. Those are also bonuses whose utility can change over the course of a campaign.

As for the flavor aspect, it depends on the GM and player. Is a familiar a companion of research and travel, who spends a lot of time with and trusts the wizard, or is it a class feature that provides useful constant bonuses? In the former case, you shouldn't allow the players to throw it away, otherwise they might be torn between the mechanical and the flavor choice.

"I'm sorry, Arthur. We spent a lot of time together and I loved you, but now I really need this +3 bonus to swim more than anything. So, goodbye, old friend."

Answer 2

The developers did notice that this permanent choice wasn't really well justified, and added the option to replace it using the (optional) Retraining rules from Ultimate Campaign:

Wizard: Retrain your arcane bond by replacing one bonded item with another, replacing your bonded item with a familiar, or replacing your familiar with a bonded item. See also retraining feats. You can instead retrain your arcane school (including changing to or from a universalist). Doing so replaces your school’s bonus spell slots and school powers. This training takes 5 days for every school power you lose from changing schools.

Regardless, every class has some permanent choices that can't easily be changed without retraining rules, like a sorcerer's bloodline, a cleric's deity and domains, a ranger's favored enemy, etc. Some of those choices offer greater benefits at lower levels than at later levels, and being able to swap between those "class-defining" abilities (like bloodlines, for instance) for free, would prove to be a great benefit for characters that have such abilities. While others, that have multiple "weaker" abilities (like fighter's bonus combat feats) wouldn't benefit too much from it.

As to why it must be the Arcane Bond, well, is there anything else? Wizards already are one of the most versatile classes in the game, second only to druids and clerics. They already can swap most of their class abilities on a day's notice. The only exception to this would be the specialization school (which is retrainable as well), and the arcane bond. But compared to other classes, they don't have many hard choices to make.