Lately, for reasons unknown even to myself, I've been re-reading Unearthed Arcana, one of the last things TSR published under Gary Gygax's byline. I'm on record as disliking it, feeling that it's a product of AD&D's creative decadence, a rococo gilding of the lily that ultimately lent credibility to many of the design decisions made in 2e. But I don't mean this post to be one about what's wrong with Unearthed Arcana but rather something that I think is right about it, or at least that might be right about it.
In this book, Gygax introduces not a new sub-class of the Thief but rather a "split class," the Thief-Acrobat. According to the text, a split class is a "specialist" thief who "leaves off all practices which increase his or her manual dexterity and begins a regimen of physical exercise in order to build coordination, muscle tone, and balance." Thieves who wish to do this must be at least 5th level and possess Strength 15 and Dexterity 16. If those requirements are met, the thief in question ceases to improve his pick pockets, open locks, find traps, and remove traps abilities (and never gains read magic) in exchange for gaining new abilities such as tumbling, tightrope walking, and high jumping. In most other respects, he remains like a normal, non-specialist thief.
What's immediately interesting to me nowadays is how similar in some ways the Thief-Acrobat is to the original conception of the paladin, which was more of a specialist fighting man than a distinct class -- meet certain requirements and you gain new abilities at the expense of others. It's an approach I've been tempted to employ in my Dwimmermount campaign, even though, to date, I've never allowed any classes beyond the cleric, fighting man, magic-user, and thief. Interestingly, this is similar to the approach Frank Mentzer adopted in his own revision of the D&D rules and one of the bits I most like about that rules set. Of course, the Thief-Acrobat is somewhat different, because it uses a different XP table than does the standard thief, a design decision that's defensible but I personally dislike, as it muddies the distinction between a split class and a sub-class.
Still, I find myself attracted to the idea of the split class as a means to create character class "specialties" without having to go the route of introducing whole sub-classes, some of which -- the druid and illusionist come immediately to mind -- involve significant rules additions. Time permitting, I may tinker with the notion of a few OD&D-style split classes and present them here for discussion. I think the split class is one of the more genuinely innovative ideas to be found within Unearthed Arcana and it's a shame it wasn't embraced more broadly in the subsequent history of the game. There may well be a reason why that's the case, but I need to explore this idea a bit more before I can decide my opinion on the matter.