how broad should an Unusual Background: Extra Option : Double Defaulter perk be?

[Plane]

PU2p20 talks about types of UB perks, which either involve being able to use advantageous rules (Extra Option) or being able to ignore disadvantageous rules.

B173 forbids double-defaulting: "A skill can’t default to another skill
known only by default."

Whether this is viewed as EO introducing an advantageous "can double default" policy or Rules Exemption excluding a disadvantageous "can't double default" policy is probably just a matter of perspective and I don't know if it matters what you would classify this as.

I've never actually seen a proposal to ignore this. Would a perk be too cheap to apply this to ALL skills? If so, what lesser number is fair?

The idea of this being it would give you limited ability in a certain amount of skills which only default to other skills and not to attributes, without requiring a point in the skills they default to.

Examples might be:

1) for casting with Ritual Magery, you don't need a point in Thaumatology to get a default in paths, instead you can apply the -6 default to the IQ-7 default in thaumatology to enjoy an IQ-13 default in the paths

2) B179 for enjoying a default in Autohypnosis you don't need Meditation, you just apply the -4 penalty to B207's Will-6 default to enjoy Autohypnosis at Will-10.

3) B209 for Metallurgy you don't need a point in Chemistry, just apply the -5 penalty to the B183 default of IQ-6 so you can do Metallurgy at IQ-11.

These penalties might also be lesser if someone has various forms of Dabbler.

[Ulzgoroth]

Considering the tremendous penalties involved, this barely seems worthwhile even at the scope of unlocking all defaults-from-defaults.

(Obviously, it would make no sense at all at the minimum scope of one point for one skill, since spending a point in either the desired skill or the skill it defaults to would be much better. I don't think there are enough things with a skill default but no attribute default to make it useful to invent an intermediate scope.)

[AlexanderHowl]

I would allow it only per default chain. So, you could take DD (Broadsword>Shortsword>Smallsword), allowing you to default Shortsword at -2 and, from Shortsword-2, defaulting to Smallsword at -6. This is equivalent to just dumping 1 CP into the intermediate skill.

[TGLS]

Well, assuming crazy high default from skills, it makes a really weird character concept. For example if you buy this:
Mathematics/TL8 (Statistics) IQ/H - IQ+20 30 [84]

You also get:
Accounting IQ/H - IQ+15 25
Administration IQ/A - IQ+2 12
Economics IQ/H - IQ+8 18
Finance IQ/H - IQ+11 21
Geography/TL8 (Political) IQ/H - IQ+4 14
Market Analysis IQ/H - IQ+3 13
Merchant IQ/A - IQ+5 15
Propaganda/TL8 IQ/A - IQ+0 10

[Anaraxes]

Originally Posted by AlexanderHowl

This is equivalent to just dumping 1 CP into the intermediate skill.

In which case, no point in making a Quirk, right? No need for a Perk to do something you can already do for a point.

I am a bit leery of making it broad, because that just encourages the Johnny One-Stat characters. (Though there are plenty of characters that seem to manage to know all about every branch of science and engineering while still at least keeping up with the rest of the adventurers, or even the occasional brainiac or literal brain-in-a-jar, those tend to make uninteresting PCs, often striking me mostly as an exercise in breaking the system.)

[AlexanderHowl]

IQ 20, Per 16, Will 16, and Science!-25 is a perfectly legal build in a cinematic campaign. Yes, it costs 244 CP, but you end up with an individual who excels in every scientific skill.

[Anaraxes]

"Legal" wasn't the point.

[Ejidoth]

Defaulting off of other defaults feels clunky and awkward enough that my normal reaction would be to ask the player to explain their character concept without referring to GURPS system terms, and then see if we can find an alternate way to build it that fits better with the system. A wildcard skill or a modular ability or something, maybe.

[pawsplay]

I wouldn't do it just because it's complicated. And possibly circular.

[Ulzgoroth]

Originally Posted by pawsplay

I wouldn't do it just because it's complicated. And possibly circular.

Circular is no problem - with large penalties at each step (with, what, one exception?), a circular default is always going to be worse than what you had before following the cycle.