Re: Why learn a martial art?
 

No, that's not unrealistic. I know when I roll with people who do BJJ they often get a little frustrated. The really good ones still own me, but the ones closer to my skill have more trouble. Their problem is that my style (Kachin Bando style grappling) is unfamiliar to them, and their style (BJJ) isn't unfamiliar to me. It's a minor advantage at best.

The combat upside of an obscure style is outweighed in a more social situation, though - my friend the BJJ blue belt can go to any BJJ school with his blue belt, tell them his instructor's name and his instructor's instructor's name, and they'll know him. They'll accept his ranking and position and skill and treat him as a blue belt.

I get tossed into the unknown category, because even after I explain my style most people still don't know what the hell I'm talking about. I'm better off saying "Kendo Shodan" and my date of ranking than explaining my years of grappling experience and fight record. It just doesn't signify as much as that minor Claim to Hospitality and Cultural Familiarity does. It helps in combat, a little, but only when I pull stuff that doesn't look like what they know.

Re: Why learn a martial art?
 

Depends on your striking Strength and your Dexterity, since if you've got no Martial Arts Style at all, that's unskilled striking (not even Brawling); personally I'd rather have access to the relevant damage bonuses and techniques. The various unarmed combat skills (and some armed ones) always tie into a "style", even if it is something as simple as "Self-defense"... which was included largely to avoid this issue in the 3e version of GURPS Martial Arts.

Having a "secret" or "new" style would be one of those Advantages with built-in Disadvantages. I'd probably just charge an appropriate Unusual Background for that. I probably wouldn't be too severe since unless the player goes through a lot of trouble, it won't remain secret for long and if it is at all effective, the player has gained a lot of unwanted attention. Don't forget the difficulty of being recognized as a martial artist (assuming you want such recognition) and the requirements for a character creating a new style (at least in 3e, it wasn't easy).

Not unless you've studied generic "Karate" as a style. I mean, some source books specifically have that - 3e Black Ops, for example, explicitly stated that the Martial Arts "style" of their agents was a distillation of all the martial arts the-powers-that-be behind the default Black Ops setting.

TL;DR: If you're campaign is bothering with the more advanced combat options that Styles apply to, then your character always has a "style". If 4e Martial Arts allows Style rules to be used without requiring a player has a style (even a placeholder like Self-Defense), color me confused.

Re: Why learn a martial art?
 

This is not the case. You can have brawling, boxing, karate, wrestling, judo, and sumo skills without having any style.

What this represents is fairly obvious...someone who's picked up the skill without studying any school (or even 'school') and thus whatever quirks their idiosyncratic style might have, nobody is going to be familiar with them.

It's slightly perverse that that character could then learn a style and in the process become predictable to all practitioners. I wonder if an additional perk would be enough to buy away the 'recognizable style' penalty.

Re: Why learn a martial art?
 

In theory there would be no reason of course why someone could not study a particular foe and spend a perk on knowing how he, in particular fights even he doesn't himself have a Style perk. Which leads inevitably to Taskmaster. Just as you can get an Unusual Background which lets you know every language in the universe you could get an Unusual Background that lets you know everyone's style provided you had an opportunity to study them.

Re: Why learn a martial art?
 

I'd think so. An additional Style Familiarity the other guy didn't have would do that after all, buying Style Familiarity (my weird personal style) doesn't seem unreasonable - somebody must have invented all of them in the first place after all.

Re: Why learn a martial art?
 

All you need to do is to get a style familiarity with a similar enough style that you don't need to learn new skills, but that is uncommon in the area. It isn't sharing a style that is the trouble, it's if your foe has style familiarities for all of your styles. If you both have the same styles, then you both have the same advantage.

And the advantage we're talking about here is only a reduction by -1 of the penalty from your foe's feints and deceptive attacks. And even this can be avoided (p. MA 49)

So learn a feint based on Dancing (which is a part of one of the martial arts in my SF setting - I call it a "graceful feint").

Re: Why learn a martial art?
 

What is the best way to handle style familiarity in campaigns where one style is very common? For example, in a campaign in medieval Europe, all knights would use the same (GURPS) style. However, I would imagine that a fighter from one region would not be able to easily read the style from a knight of another school / region.
What is the best way to handle this? Split the style into sub styles that are the same in GURPS terms but don't have style familiarity between them? Or just to limit the style perk?

Re: Why learn a martial art?
 

I would use your first suggestion, splitting them into similar styles (same skills, but maybe a different technique or two) based on region. Knights who actually use their arts and practice should have a style.

Re: Why learn a martial art?
 

I'm not sure, what's the justification real-world? "I get rid of my recognizable tactics and replace them with tactics no one has ever seen before" is just . . . odd. I'm not sure what that would be. I know beginners can throw off trained people because they do aggressively stupid things which can catch you off guard, but that's not the same thing - it's not really any different than fighting someone who is doing those things on purpose when they are using a style you've never seen before.

Learning a true additional style to throw people off is valid - and I've seen it. When I was in Japan one of my co-workers did sport Capoeira. A Kudo instructor came to his informal class to learn some moves he could insert into his own style to throw people off at the next tournament. It worked too. He went from "fighting guys who know his style" to "using a style they aren't familiar with."

For people who really want a total "includes all, but familiar to none" go with Ultimate Fighting, on MA p. 20. For 20 points you buy Style Familiarity with everything; but only other Ultimate Fighting stylists count as familiar with your style. Yes, it's 29 points including the style, but learning to fight like Remo Williams isn't cheap. ;)

Re: Why learn a martial art?
 

That would not actually do anything. It's the technique used after the feint, not the technique used for the feint.
Well, the semi-real-world justification is that before you spent one point buying style familiarity, your character's deceptive attacks were better, in a way that is, technically, impossible for your character to ever experience again after they've bought a single style familiarity.

So by stepping into a dojo somewhere and getting a white belt, you permanently lose your personal fighting patterns, which worked perfectly well up until then? The inspiration here, remember, is a character who was an accomplished fighter before they learned any style. The idea is that they're basically claiming a style familiarity with an undocumented style which has no co-stylists and no optional traits, skills, techniques, or perks they don't already know.

For someone who learned a style first, clearly it's not impossible to still invent an idiosyncratic way of doing things that nobody's seen before. But it's probably hard and likely not as appealing as actually picking up a new style familiarity, which is almost as good and has additional benefits.

...Huh, I think the familiarity rule might have a slight issue. There's no filter on the styles that are considered, which means that having familiarity with Kusarijutsu or Foot Archery can thwart the other guy's familiarity in an unarmed fight. Perhaps only familiarities that include the skill you're using should count... Or even only styles that include the specific technique you're using.