A thought game, really. Most class features are on par with those that are swapped out with other class features as given by archtypes.
From a game balance standpoint, I'm curious as to how 'broken' things would be if a house rule allowed regular class features to be retrained individually (following obvious dependencies) with archetype features of the same level.
Anyone ever done this?
Most archetype abilities are either
A) balanced by you giving up other powerful options
B) made functional by other class abilities.
I'm sure there are still some game breaking combination just because there would be so many possible combinations.
Potentially, it could be very broken. Conversely, it doesn't have to be.
An archetype might give up class features A, B and C, whilst gaining D, E and F.
In total, they should be balanced, but A and F might be better than all 4 of the others put together.
Grudgekeyper has the right idea.
Depends on the class.
That's the basic idea behind the Talented Fighter from Genius games. All the archetype abilities are available to be taken in feat style. The result is a more customizable fighter, but not noticeably more powerful.
I was considering running a game based on this concept.
As others have said, it does matter a little which class we're looking at.
Overall, IMHO, this wouldn't be broken, though. Just be careful of weirdness. As always.
On a related note, I was looking at running a game that used a modified gestalt rule: you could choose one archetype and gain its benefits on top of the normal class features. You could choose a second archetype, but you would treat your modified class as the base class.
The strangest interactions with this model occurred in the Summoner.
This is similar to what 3.5 started doing, with racial/class substitution levels, at least if I understand it right. Those only usually had 3 levels and specific options. This could be quite good...or break quite badly.
For example, I might love to get back well-versed and versatile performance for my arcane duelist, so I might trade out bladethirst and mass bladethirst. Why? I'll make plenty more skill checks in this Skull & Shackles campaign, but by the time I start getting those abilities online, they won't necessarily be worth it. Mind you, this is just me thinking of something right off the bat. For classes people generally consider weaker (e.g. rogues, fighters, monks), it might work in their favor. I'd have to see what broken things this enables for more versatile/flexible classes (e.g. shaman).
This demonstrates the need for point buy building, like in Mutants & Masterminds -- more powerful abilities get higher point costs, so you can't get as many of them.
Short of that, one possibility would be to expand the VMC system(*) to include archetypes: instead of just having 1 VMC for each class, you have the option of taking a VMC of an archetype of that class (**). In addition, you would be allowed to take VMC of the same class as your primary class (or one of your primary/secondary classes), although numeric benefits from getting the same class features again (such as Weapon Training, Sneak Attack, or Channel Energy) would typically be capped by your hit dice(***), so that it would usually make more sense to do this with archetypes that substitute the abilities that would otherwise get capped by attempting to stack beyond your hit dice limit (although if you just dipped in a primary/secondary class, then taking VMC of the same archetype could make sense). For instance, you could go Fighter (unarchetyped) VMC Tower Shield Specialist Fighter or Tower Shield Specialist Fighter VMC Fighter (unarchetyped), depending upon how much you wanted to focus on the Tower Shield specialty; this combination would suffer a bit from Armor Training in excess of the numeric bonuses allowed by your total hit dice unless you were just dipping in the non-VMC Fighter variety, although you would still get the full benefit of having more Advanced Armor Training options (when the Armor Master's Handbook comes out), so the extra Armor Training ranks wouldn't be a complete waste. But it would usually be more optimal to do something like Lore Warden Fighter VMC Tower Shield Specialist Fighter or Tower Shield Specialist Fighter VMC Lore Warden Fighter, to avoid running up against the numeric cap.
(*)Actually, first clean it up and balance it -- the quality of the current VMC options is really uneven, ranging from awesome options (like VMC Wizard and VMC Magus, and even VMC Fighter is starting to look not too shabby with the Weapon Master's Handbook) to really terrible (VMC Gunslinger, VMC Ranger, VMC Witch, and usually VMC Monk, although the latter could work for really specific cases like certain Ninja builds).
(**)Not necessarily a 1-to-1 correspondence, since VMC doesn't give as many ranks of class features as the parent class and often doesn't give as many features overall, so not all archetype substitutions make sense, and some of those that do make sense end up becoming the same thing as each other.
(***)For some things like Weapon Training, figuring the cap based upon total Base Attack Bonus might make more sense than hit dice.
Sorry if this is obvious to everyone but me, but what does "VMC" stand for?
Variant Multi Classing. Spend feats to get some of another class' features.
Oh, okay.